Semi-Empirical Theory of the Nuclear Energy Surface

1947 ◽  
Vol 19 (3) ◽  
pp. 239-258 ◽  
Author(s):  
Eugene Feenberg
Keyword(s):  
Nuclear Energy ◽  
Energy Surface ◽  
Empirical Theory ◽  
Semi Empirical

Numerical Study on Air-Reed Instruments With LES

2011 ◽  
Author(s):  
Kin’ya Takahashi ◽  
Masataka Miyamoto ◽  
Yasunori Ito ◽  
Toshiya Takami ◽  
Taizo Kobayashi ◽  
...  
Keyword(s):  
Numerical Study ◽  
Sound Field ◽  
Acoustic Analogy ◽  
Empirical Theory ◽  
Sound Sources ◽  
Aerodynamic Sound ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Semi Empirical ◽  
2D And 3D

The acoustic mechanisms of 2D and 3D edge tones and a 2D small air-reed instrument have been studied numerically with compressible Large Eddy Simulation (LES). Sound frequencies of the 2D and 3D edge tones obtained numerically change with the jet velocity well following Brown’s semi-empirical equation, while that of the 2D air-reed instrument behaves in a different manner and obeys the semi-empirical theory, so called Cremer-Ising-Coltman theory. We have also calculated aerodynamic sound sources for the 2D edge tone and the 2D air-reed instrument relying on Ligthhill’s acoustic analogy and have discussed similarities and differences between them. The sound source of the air-reed instrument is more localized around the open mouth compared with that of the edge tone due to the effect of the strong sound field excited in the resonator.

Geometry optimizations with the incremental molecular fragmentation method

2018 ◽  
Vol 17 (05) ◽  
pp. 1850037 ◽  
Author(s):  
Oinam Romesh Meitei ◽  
Andreas Heßelmann
Keyword(s):  
Nuclear Energy ◽  
Energy Surface ◽  
Chem Phys ◽  
Theory Method ◽  
Molecular Fragmentation ◽  
Hartree Fock ◽  
Moller Plesset ◽  
Derivatives Of ◽  
Plesset Perturbation Theory ◽  
The Imf

Nuclear energy gradients for the incremental molecular fragmentation (IMF) method presented in our previous work [Meitei OR, Heßelmann A, Molecular energies from an incremental fragmentation method, J Chem Phys 144(8):084109, 2016] have been derived. Using the second-order Møller–Plesset perturbation theory method to describe the bonded and nonbonded energy and gradient contributions and the uncorrelated Hartree–Fock method to describe the correction increment, it is shown that the IMF gradient can be easily computed by a sum of the underlying individual derivatives of the energy contributions. The performance of the method has been compared against the supermolecular method by optimizing the structures of a range of polyglycine molecules with up to 36 glycine residues in the chain. It is shown that with a sensible set of parameters used in the fragmentation the supermolecular structures can be fairly well reproduced. In a few cases the optimization with the IMF method leads to structures that differ from the supermolecular ones. It was found, however, that these are more stable geometries also on the supermolecular potential energy surface.

scholarly journals Modeling of Deposition of Solid Particles at Cleaning of Oil in Gravitational Separator

2020 ◽  
Vol 126 (1) ◽  
pp. 8-10
Author(s):  
А. А. Gasanov ◽  
◽  
N. Kh. Gamzaeva ◽  
Keyword(s):  
Particle Deposition ◽  
Stationary Process ◽  
Viscous Friction ◽  
Added Mass ◽  
Solid Particles ◽  
Mass Force ◽  
Empirical Theory ◽  
Friction Forces ◽  
Proposed Model ◽  
Semi Empirical

The non-stationary process of sedimentation of a solid spherical particle in a fluid at rest in a gravitational separator is considered. To describe this process, we propose a mathematical model that takes into account viscous friction forces, which is determined on the basis of the Prandtl semi-empirical theory of turbulence, Basse hereditary force, as well as the added mass force. To implement the proposed model, a difference method is used. Using a numerical experiment, the effects of various forces on the particle deposition rate are investigated.

scholarly journals Theoretical study of the potential energy surface of N-formyl-L-cysteine-amide by using a genetic algorithm multi niche crowding

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Genetic Algorithm ◽  
Energy Surface ◽  
Energy Analysis ◽  
Theoretical Study ◽  
Molecular Structures ◽  
Conformational Space ◽  
Side Chain ◽  
Am1 Method ◽  
The Subject ◽  
Semi Empirical

The generation of molecular structures constituting the conformational space of trans-N-For-L-Cys-NH2 was accomplished using the genetic algorithm MNC coupled to the semi-empirical AM1 method, AM1/GA-MNC. The structural and energy analysis of the obtained conformational space E=E(,ψ) locates 7 regions or minima ɣL, ɣD, L, D, L, ɛD and ɛL. The combination of these folds to structuring modes adopted by the side chain CH2-SH has allowed us to identify 27 stable geometric structures. The regions corresponding to helical folds αD and αL are not favorable for the system that is the subject of current study.

Polyalanine gas phase acidities determination and conformational space analysis by genetic algorithm assessment

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Genetic Algorithm ◽  
Gas Phase ◽  
Energy Surface ◽  
Conformational Space ◽  
Am1 Method ◽  
The One ◽  
Semi Empirical ◽  
Global And Local ◽  
Formation Energies ◽  
Good Agreement

The genetic algorithm, based on the Multi-Niche Crowding (MNC) method, coupled with the semi-empirical AM1 method is used to analyze the potential energy surface of some polypeptides containing cysteine. Calculating the formation energies of these systems in both neutral and deprotonated states, we deducted their enthalpy of deprotonation (ΔHacid) and we identified the types of rearrangement of these systems when isolated. Deprotonation occurs at the level of the alone acid site characterizing these peptides namely the thiol. The values obtained for the deprotonation enthalpies of polypeptides AlaCysNH2, Ala2CysNH2, Ala3CysNH2, Ala4CysNH2, CysAlaNH2 and CysAla2NH2 are in the order of 331.3 kcal/mol, 322.9 kcal/mol, 313.8 kcal/mol, 312.9 kcal/mol, 325.1 kcal/mol and 317.3 kcal/mol, respectively. The location of global and local minima of these polypeptides shows that they are rearranged in two forms of secondary structures namely helical and globular forms. The obtained results are in good agreement with the experimental ones, on the one hand, and with those from other methods in the theoretical calculation, on the other hand. Therefore, the N-cysteine is more acidic than their homologous C-Cysteine and for this series of plolyalanines, the acidity in the gas phase increased with the peptide chain length.

Conformational space analysis of neutral and protonated glycine using a genetic algorithm for multi-modal search

2014 ◽  
Vol 13 (08) ◽  
pp. 1450067 ◽  
Author(s):  
B. El Merbouh ◽  
M. Bourjila ◽  
R. Tijar ◽  
R. Drissi El Bouzaidi ◽  
A. El Gridani ◽  
...  
Keyword(s):  
Genetic Algorithm ◽  
Potential Energy ◽  
Potential Energy Surface ◽  
Energy Surface ◽  
Protonated Form ◽  
Conformational Space ◽  
Empirical Methods ◽  
Space Analysis ◽  
Semi Empirical

The genetic algorithm based on the Multi-Niche Crowding (MNC) method is used with the semi-empirical methods AM1 and PM3 in order to scan the potential energy surface (PES) of neutral and protonated glycine. The algorithm is implemented as a package of programs interfaced with MOPAC and piloted by scripts. Both methods AM1 and PM3 located six minima on the PES of neutral glycine and seven on the protonated glycine one, of which three are those of the N -protonated form and four of the O -protonated one.

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