Criterion of Mechanical Instability in Inhomogeneous Atomic System

2005 ◽  
Vol 482 ◽  
pp. 127-130 ◽  
Author(s):  
Yoshitaka Umeno ◽  
Takayuki Kitamura
Keyword(s):  
Mechanical Stability ◽  
Atomic System ◽  
Instability Criterion ◽  
Fundamental Issue ◽  
Mechanical Instability ◽  
Atomic Systems ◽  
Uniform Deformation ◽  
Atomic Structures ◽  
Homogeneous Structures ◽  
Deformation Modes

The mechanical stability of a material is a fundamental issue in strength of atomic systems. Although the criterion of the mechanical stability of homogeneous structures such as perfect crystals have been successfully investigated so far, the criterion has not been able to be precisely evaluated in the cases of non-uniform deformations or bodies of inhomogeneous atomic structures. Now we present an instability criterion of an arbitrary atomic structure based on the energy balance of the whole system. This method gives the mathematically rigorous condition for the onset of an unstable deformation in any inhomogeneous atomic system. Furthermore, the method can be applied to any type of potential field, which means that ab initio evaluations of the mechanical instability of inhomogeneous structure under non-uniform deformation will be possible. The validity of the method is clarified by the application to tension of a cracked body. The onsets of unstable deformations and their deformation modes are precisely evaluated by the method.

scholarly journals Mechanical Stability of Hybrid Corrugated Sandwich Plates under Fluid-Structure-Thermal Coupling for Novel Thermal Protection Systems

2020 ◽  
Vol 10 (8) ◽  
pp. 2790
Author(s):  
Wenzheng Zhuang ◽  
Chao Yang ◽  
Zhigang Wu
Keyword(s):  
Mechanical Stability ◽  
Thermal Protection ◽  
Element Model ◽  
Parameter Study ◽  
The Novel ◽  
Thermal Coupling ◽  
Mechanical Instability ◽  
Fluid Structure ◽  
Thermal Protection Systems ◽  
Protection Systems

Hybrid corrugated sandwich (HCS) plates have become a promising candidate for novel thermal protection systems (TPS) due to their multi-functionality of load bearing and thermal protection. For hypersonic vehicles, the novel TPS that performs some structural functions is a potential method of saving weight, which is significant in reducing expensive design/manufacture cost. Considering the novel TPS exposed to severe thermal and aerodynamic environments, the mechanical stability of the HCS plates under fluid-structure-thermal coupling is crucial for preliminary design of the TPS. In this paper, an innovative layerwise finite element model of the HCS plates is presented, and coupled fluid-structure-thermal analysis is performed with a parameter study. The proposed method is validated to be accurate and efficient against commercial software simulation. Results have shown that the mechanical instability of the HCS plates can be induced by fluid-structure coupling and further accelerated by thermal effect. The influences of geometric parameters on thermal buckling and dynamic stability present opposite tendencies, indicating a tradeoff is required for the TPS design. The present analytical model and numerical results provide design guidance in the practical application of the novel TPS.

scholarly journals On detour index of cycloparaphenylene and polyphenylene molecular structures

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
S. Prabhu ◽  
Y. Sherlin Nisha ◽  
M. Arulperumjothi ◽  
D. Sagaya Rani Jeba ◽  
V. Manimozhi
Keyword(s):  
Atomic System ◽  
Molecular Structures ◽  
Topological Descriptors ◽  
Covalent Bonds ◽  
Atomic Structures ◽  
Topological Descriptor ◽  
Structure Activity ◽  
Mathematical Correlation ◽  
Benzene Rings ◽  
Unique Method

AbstractCycloparaphenylene is a particle that comprises a few benzene rings associated with covalent bonds in the para positions to frame a ring-like structure. Similarly, poly (para-phenylenes) are macromolecules that include benzenoid compounds straightforwardly joined to each other by C–C bonds. Because of their remarkable architectural highlights, these structures have fascinated attention from numerous vantage focuses. Descriptors are among the most fundamental segments of prescient quantitative structure-activity and property relationship (QSAR/QSPR) demonstrating examination. They encode chemical data of particles as quantitative numbers, which are utilized to create a mathematical correlation. The nature of a predictive model relies upon great demonstrating insights, yet additionally on the extraction of compound highlights. To a great extent, Molecular topology has exhibited its adequacy in portraying sub-atomic structures and anticipating their properties. It follows a two-dimensional methodology, just thinking about the interior plan, including molecules. Explicit subsets speak the design of every atom of topological descriptors. When all around picked, these descriptors give a unique method of describing an atomic system that can represent the most significant highlights of the molecular structure. Detour index is one such topological descriptor with much application in chemistry, especially in QSAR/QSPR studies. This article presents an exact analytical expression for the detour index of cycloparaphenylene and poly (para-phenylene).

scholarly journals Frames for operators in Banach spaces via semi-inner products

2016 ◽  
Vol 14 (03) ◽  
pp. 1650011 ◽  
Author(s):  
Bahram Dastourian ◽  
Mohammad Janfada
Keyword(s):  
Banach Space ◽  
Banach Spaces ◽  
Reproducing Kernel ◽  
Atomic System ◽  
Inner Product ◽  
Reconstruction Formula ◽  
Frame Operator ◽  
Atomic Systems ◽  
Perturbation Result ◽  
Reproducing Kernel Banach Spaces

In this paper, the concept of a family of local atoms in a Banach space is introduced by using a semi-inner product (s.i.p.). Then this concept is generalized to an atomic system for operators in Banach spaces. We also give some characterizations of atomic systems leading to new frames for operators. In addition, a reconstruction formula is obtained. The characterizations of atomic systems allow us to state some results for sampling theory in s.i.p reproducing kernel Banach spaces. Finally, we define the concept of frame operator for these kinds of frames in Banach spaces and then we establish a perturbation result in this framework.

scholarly journals OPTIMIZED QUASIPARTICLE DENSITY FUNCTIONAL APPROACH FOR MULTIELECTRON ATOMIC SYSTEMS

2021 ◽  
pp. 38-44
Author(s):  
A. Glushkov ◽  
V. Kovalchuk ◽  
A. Sofronkov ◽  
A. Svinarenko
Keyword(s):  
Density Functional ◽  
Atomic System ◽  
Mass Operator ◽  
Fermi Liquids ◽  
Dft Theory ◽  
Functional Theory ◽  
Atomic Systems ◽  
Hartree Fock ◽  
The Third ◽  
Quasiparticle Density

We present the optimized version of the quasiparticle density functional theory (DFT), constructed on the principles of the Landau-Migdal Fermi-liquids theory and principles of the optimized one-quasiparticle representation in theory of multielectron systems. The master equations can be naturally obtained on the basis of variational principle, starting  from a Lagrangian of an atomic system as a functional of  three quasiparticle densities. These densities  are similar to the Hartree-Fock (HF)  electron density and kinetical energy density correspondingly, however the third density  has no an analog in the Hartree-Fock or the standard  DFT theory and appears as result of account for the energy dependence of the mass operator S. The elaborated  approach to construction of the eigen-functions basis can be characterized as an improved one in comparison with similar basises of other one-particle representations, namely, in the HF,  the standard Kohn-Sham approximations etc.

scholarly journals Effect of Morphology and Mechanical Stability of Nanometric Platinum Layer on Nickel Foam for Hydrogen Evolution Reaction

Energies ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 3116
Author(s):  
Rachela G. Milazzo ◽  
Stefania M. S. Privitera ◽  
Silvia Scalese ◽  
Salvatore A. Lombardo
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Deposition Time ◽  
Mechanical Stability ◽  
Nickel Foam ◽  
Linear Sweep Voltammetry ◽  
Electrochemical Activity ◽  
Alkaline Electrolyte ◽  
Mechanical Instability ◽  
Platinum Layer

Platinum thin films are deposited on open-cell nickel foam with porosity of 95% via spontaneous galvanic displacement. Ni foams with different morphologies and pore size are compared and characterized by electrochemical and structural analysis techniques. The effect of Pt coating on the electrochemical activity is studied by using the Pt coated foam as electrode material for hydrogen evolution reaction in an aqueous alkaline electrolyte. The electrocatalytic activity of the electrodes is evaluated using linear sweep voltammetry curves and Tafel plots as a function of deposition time. The comparison with scanning electron microscopy analyses demonstrates that the catalytic activity has a maximum when the platinum film completely covers the Ni surface. The further increase of the Pt thickness leads to mechanical instability with crack formation and delamination. The effect of the foam morphology on the Pt deposition rate has been evaluated and discussed, determining the minimum Pt amount required to achieve the maximum electrochemical activity, as well as the maximum thickness in order to assure stable characteristics before delamination occurs.

scholarly journals EFFECTS OF GEOMETRIC VARIATIONS ON THE BUCKLING OF ARTERIES

2011 ◽  
Vol 03 (02) ◽  
pp. 385-406 ◽  
Author(s):  
PARAG DATIR ◽  
AVIONE Y. LEE ◽  
SHAWN D. LAMM ◽  
HAI-CHAO HAN
Keyword(s):  
Cross Sections ◽  
Critical Pressure ◽  
Arterial Wall ◽  
Mechanical Stability ◽  
Longitudinal Axis ◽  
Nonlinear Material ◽  
Mechanical Instability ◽  
Element Analysis ◽  
Buckling Behavior ◽  
Oval Cross Section

Arteries often demonstrate geometric variations such as elliptic and eccentric cross sections, stenosis, and tapering along the longitudinal axis. Effects of these variations on the mechanical stability of the arterial wall have not been investigated. The objective of this study was to determine the buckling behavior of arteries with elliptic, eccentric, stenotic, and tapered cross sections. The arterial wall was modeled as a homogeneous anisotropic nonlinear material. Finite element analysis was used to simulate the buckling process of these arteries under lumen pressure and axial stretch. Our results demonstrated that arteries with an oval cross section buckled in the short axis direction at lower critical pressures as compared to circular arteries. Eccentric cross sections, stenosis, and tapering also decreased the critical pressure. Stenosis led to dramatic pressure variations along the vessel and reduced the buckling pressure. In addition, tapering shifted the buckling deformation profile of the artery towards the distal end. We conclude that geometric variations reduce the critical pressure of arteries and thus make the arteries more prone to mechanical instability than circular cylindrical arteries. These results improve our understanding of the mechanical behavior of arteries.

scholarly journals Two-body corrections to the g factors of the bound muon and nucleus in light muonic atoms

2019 ◽  
Vol 73 (10) ◽  
Author(s):  
Savely G. Karshenboim ◽  
Vladimir G. Ivanov
Keyword(s):  
Electrostatic Interaction ◽  
Coulomb Potential ◽  
Atomic System ◽  
Magnetic Moments ◽  
Master Equations ◽  
Atomic Systems ◽  
Muonic Atoms ◽  
Pure Coulomb ◽  
Coulomb Effects ◽  
Three Body

Abstract A nonrelativistic (NR) theory of recoil corrections to the magnetic moments of bound particles is revisited. A number of contributions can be described within an NR theory with the help of various potentials. We study those potential-type contributions for two-body atomic systems. We have developed an approach, that allows us to find the g factor for an electron or muon in a two-body bound system for an arbitrary electrostatic interaction together with the m/M recoil corrections, as well as the binding corrections to the g factor of the nucleus. We focus our attention on light muonic two-body atoms, where the recoil effects are enhanced. Both mentioned kinds of contributions have been previously known only for the pure Coulomb effects. We have applied the here-obtained master equations to a few particular cases of perturbations of the Coulomb potential. In particular, the results on the recoil corrections to the finite-nuclear-size (FNS) and Uehling-potential contributions to the g factor of the bound muon are obtained. The Uehling-potential and FNS contributions to the g factor of the bound nucleus have been found as well together with the related recoil corrections. We have generalized the results for the case of the g factor of a bound muon in a three-body atomic system consisting of an electron, a muon, and a spinless nucleus. Graphical abstract

THE EFFECT OF METAL-MOLECULE NANO-CONTACTS WITH DIFFERENT END GROUPS IN MOLECULAR ELECTRONICS

2009 ◽  
Vol 23 (30) ◽  
pp. 5657-5669 ◽  
Author(s):  
SEIFOLLAH JALILI ◽  
ABDOLHAKIM PANGH
Keyword(s):  
Electron Transport ◽  
Molecular Electronics ◽  
Atomic System ◽  
Transmission Function ◽  
Molecular Wires ◽  
Atomic Systems ◽  
Current Voltage ◽  
Electron Transport Properties ◽  
Current Voltage Characteristics ◽  
Function Density

We investigated the electron transport properties of thiophen-bithiol-based molecular wires through atomic metal–thiophen–metal systems using the first principle methods. Various metal–thiophen–metal atomic systems are constructed with different end atoms (S, Se, and Te). The electron transport of the atomic system is systematically studied by analysis of transmission function, density of states, and current–voltage characteristics of the systems.

scholarly journals Waterfall ice: mechanical stability of vertical structures

2011 ◽  
Vol 57 (203) ◽  
pp. 407-415 ◽  
Author(s):  
J. Weiss ◽  
M. Montagnat ◽  
B. Cinquin-Lapierre ◽  
P.A. Labory ◽  
L. Moreau ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Low Temperatures ◽  
Mechanical Stability ◽  
Pressure Fluctuations ◽  
Northern Italy ◽  
Temperature Cycle ◽  
Internal Stresses ◽  
Air Cooling ◽  
Mechanical Instability ◽  
Photographic Survey

AbstractWe present a study of the mechanical (in)stability of the ephemeral waterfall ice structures that form from the freezing of liquid water seeping on steep rock. Three vertical structures were studied, two near Glacier d’Argentière, France, and one in the Valsavarenche valley, northern Italy. The generation of internal stresses in the ice structure in relation to air- and ice-temperature conditions is analyzed from pressure sensor records. Their role in the mechanical instability of the structures is discussed from a photographic survey of these structures. The main result is that dramatic air cooling (several °Ch−1 over several hours) and low temperatures (<−10°C), generating tensile stresses and brittleness, can trigger a spontaneous or climber-induced mechanical collapse, leading to unfavorable climbing conditions. Ice internal pressure fluctuations are also associated with episodes of marked diurnal air-temperature cycle, with mild days (few above 0) and cool nights (few below 0), through the occurrence of water ↔ ice phase transitions within the structure. These ice internal stress fluctuations seem, however, to have a local influence, are associated with warm (near 0), wet and therefore particularly soft ice and do not trigger a collapse of the structure.

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