Search results for "Free Energy"
showing 10 items of 170 documents
Zur Frage der Charakterisierung stationärer Bewegungen in der Hydrodynamik
1958
Helmholtz andKorteweg propose that the steady motion of a viscous fluid under constant extraneous forces having a single-valued potential dissipates—for any given region and assuming that inertia terms in the dynamic equations can be neglected—less energy than any other motion with the same values of velocity at the boundary.—A generalization of this proposition is here given, and an application discussed. The application deals with the motion of a simple macromolecule model in an inhomogeneous field of flow—a motion caused only by the influence ofStokes' friction.
Resonant Kelvin-Helmholtz modes in sheared relativistic flows
2007
Qualitatively new aspects of the (linear and non-linear) stability of sheared relativistic (slab) jets are analyzed. The linear problem has been solved for a wide range of jet models well inside the ultrarelativistic domain (flow Lorentz factors up to 20; specific internal energies $\approx 60c^2$). As a distinct feature of our work, we have combined the analytical linear approach with high-resolution relativistic hydrodynamical simulations, which has allowed us i) to identify, in the linear regime, resonant modes specific to the relativistic shear layer ii) to confirm the result of the linear analysis with numerical simulations and, iii) more interestingly, to follow the instability develo…
NON-LINEAR MECHANICAL, ELECTRICAL AND THERMAL PHENOMENA IN PIEZOELECTRIC CRYSTALS
2003
Mechanical, electrical and thermal phenomena occurring in piezoelectric crystals were examined by non-linear approximation. For this purpose, use was made of the thermodynamic function of state, which describes an anisotropic body. Considered was the Gibbs function. The calculations included strain tensor εij = f(σkl , En, T), induction vector Dm = f(σkl , En, T) and entropy S = f(σkl , En, T) as function of stress σkl , field strength En and temperature difference T. The equations obtained apply to anisotropic piezoelectric bodies provided that the “forces” σkl , En, T acting on the crystal are known. Механічні, електричні та термічні явища у п’єзоелектричних кристалах вивчаються у неліній…
On the merit of a Central Limit Theorem-based approximation in statistical physics
2012
The applicability conditions of a recently reported Central Limit Theorem-based approximation method in statistical physics are investigated and rigorously determined. The failure of this method at low and intermediate temperature is proved as well as its inadequacy to disclose quantum criticalities at fixed temperatures. Its high temperature predictions are in addition shown to coincide with those stemming from straightforward appropriate expansions up to (k_B T)^(-2). Our results are clearly illustrated by comparing the exact and approximate temperature dependence of the free energy of some exemplary physical systems.
Reference beam dynamics layout for the SC CW heavy ion HELIAC at GSI
2020
Abstract The standalone superconducting continuous wave heavy ion linac HELIAC (HElmholtz LInear ACcelerator) is a common project of GSI Helmholtz Centre for Heavy Ion Research and Helmholtz Institute Mainz (HIM) under key support of Goethe University Frankfurt (IAP) and in collaboration with National Research Nuclear University MEPhI and NRC “Kurchatov Institute” ITEP. In 2017 the first superconducting section of the linac has been successfully commissioned and extensively tested with beam at GSI. The measurements sufficiently present the capability of 216.816 MHz multi-gap Crossbar H-mode (CH) DTL-structures. An acceleration of heavy ions up to the design beam energy and beyond has been r…
A dynamic collimation and alignment system for the Helmholtz linear accelerator
2021
Review of scientific instruments 92(11), 113306 - 113306-9 (2021). doi:10.1063/5.0069824
Stability of Relativistic Hydrodynamical Planar Jets: Linear and Nonlinear Evolution of Kelvin-Helmholtz Modes
2004
Some aspects about the stability of relativistic flows against Kelvin-Helmholtz (KH) perturbations are studied by means of relativistic, hydrodynamical simulations. In particular, we analyze the transition to the fully nonlinear regime and the long-term evolution of two jet models with different specific internal energies.
Spin Transition in Iron Compounds
1984
First-row transition metal complexes with d4 up to d7 electron configuration in octahedral ligand fields (and d8 electron configuration in six-coordinate complexes of lower symmetry) may undergo temperature dependent high spin (HS) ⇌ low spin (LS) transition, provided the ligand field strength (Δ), including low symmetry contributions, becomes comparable in magnitude with the mean spin pairing energy (P). At a critical field strength Δcrit = P, the energy levels of the two spin states cross. This is illustrated in Fig. 1, where a simplified Tanabe-Sugano type energy level diagram for d6 systems (e.g. Fe2+, Co3+) is shown as an example. For weak ligand fields, Δ Δcrit, the LS state1A1g(Oh) b…
Mapping CO diffusion paths in Myoglobin with the Single Sweep Method
2010
The pathways of diffusion and escape of a CO molecule inside and out a myoglobin protein are investigated. Specifically, the three-dimensional potential of mean force (PMF or free energy) of the CO molecule position inside the protein is calculated by using the single-sweep method in concert with fully resolved atomistic simulations in explicit solvent.The results are interpreted under the assumption that the diffusion of the ligand can be modeled as a navigation on the PMF in which the ligand hops between the PMF local minima following the minimum free energy paths (MFEPs) with rates set by the free energy barriers that need to be crossed. We calculate all these quantities --local minima, …
Excess free energy of nanoparticles in a polymer brush
2008
Abstract We present an efficient method for direct determination of the excess free energy Δ F of a nanoparticle inserted into a polymer brush. In contrast to Widom's insertion method, the present approach can be efficiently implemented by Monte Carlo or Molecular Dynamics methods also in a dense environment. In the present investigation the method is used to determine the free energy penalty Δ F ( R , D ) for placing a spherical particle with an arbitrary radius R at different positions D between the grafting plane and the brush surface. Deep inside the brush, or for dense brushes, one finds Δ F ∝ R 3 whereas for shallow nanoclusions Δ F ∝ R 2 , regardless of the particle interaction (…