Search results for "INTEGRATION"
showing 10 items of 1465 documents
Generalized Langevin dynamics: construction and numerical integration of non-Markovian particle-based models.
2018
We propose a generalized Langevin dynamics (GLD) technique to construct non-Markovian particle-based coarse-grained models from fine-grained reference simulations and to efficiently integrate them. The proposed GLD model has the form of a discretized generalized Langevin equation with distance-dependent two-particle contributions to the self- and pair-memory kernels. The memory kernels are iteratively reconstructed from the dynamical correlation functions of an underlying fine-grained system. We develop a simulation algorithm for this class of non-Markovian models that scales linearly with the number of coarse-grained particles. Our GLD method is suitable for coarse-grained studies of syste…
Computing absolute free energies of disordered structures by molecular simulation
2009
We present a Monte Carlo simulation technique by which the free energy of disordered systems can be computed directly. It is based on thermodynamic integration. The central idea is to construct an analytically solvable reference system from a configuration which is representative for the state of interest. The method can be applied to lattice models (e.g., the Ising model) as well as off-lattice molecular models. We focus mainly on the more challenging off-lattice case. We propose a Monte Carlo algorithm, by which the thermodynamic integration path can be sampled efficiently. At the examples of the hard sphere liquid and a hard disk solid with a defect, we discuss several properties of the …
Elementary theory and brief history
1991
In the history of the theory of deuteron photodisintegration one may distinguish roughly three periods: (i) the primitive period of the elementary theory using very simple wave functions and forces and considering lowest multipoles (E1, M1) only, (ii) the classical period still in the framework f conventional nuclear physics, but using realstic forces with correspondingly elaborate wave functions and considering also higher multipole transitions, (ii) the post-classic period with explicit treatment of subnuclear degrees of freedom like meson and isobar degrees of freedom and very recently quark-gluon degrees of freedom.
SU-E-T-343: Valencia Applicator Commissioning Using a Micro-Chamber Array
2014
Purpose: In the commissioning and QA of surface isotope-based applicators, source-indexer distance (SID) has a great influence in the flatness, symmetry and output. To these purposes, methods described in the literature are the use of a special insert at the entrance of dwell chamber or radiochromic films. Here we present the experience with a micro-chamber array to perform the commissioning and QA of Valencia applicators. Methods: Valencia applicators have been used, the classic and the new extra-shielded version. A micro-chamber array has been employed, 1000 SRS (PTW), with 977 liquid filled, 2.3×2.3×0.5 mm3 sized ion chambers covering 11×11 cm2, which spacing is 2.5 mm in the central 5.5…
Full Wave Solution for Intel CPU With a Heat Sink for EMC Investigations
2010
A CPU with a heat sink (e.g. Intel Pentium 4 and Intel Pentium dual core) is a challenging problem for EMC analysis. A Very Large Scale Integrated (VLSI) device was modelled using the Finite Element Method (FEM) frequency domain solver to obtain a 3D full wave solution. The electromagnetic (EM) radiation emitted from these high power microelectronic circuits connected to a heat sink was found to have resonant frequencies around 2.4 GHz and 5 GHz with reflection coefficients less than -19 dB and -8 dB respectively. These resonant frequencies are very close to the operating frequency of both IEEE and Bluetooth wireless communication systems. This paper proposes a new benchmark model based on …
Time-Domain Integration of Terahertz pulses
2021
We report on the time-domain integration of terahertz pulses obtained via the tight confinement of the radiation in a tapered two-wire waveguide. Both simulation and experimental results prove the time integration capability of this structure.
Tapered Two-Wire Waveguide for Time-Domain Integration of Broadband Terahertz Pulses
2021
We show the time-domain integration of terahertz pulses achieved in a sub-wavelength, tapered two-wire waveguide. Both simulation and experimental results prove the time integration functionality of this waveguide topology.
Scaling of non-Markovian Monte Carlo wave-function methods
2004
We demonstrate a scaling method for non-Markovian Monte Carlo wave-function simulations used to study open quantum systems weakly coupled to their environments. We derive a scaling equation, from which the result for the expectation values of arbitrary operators of interest can be calculated, all the quantities in the equation being easily obtainable from the scaled Monte Carlo simulations. In the optimal case, the scaling method can be used, within the weak coupling approximation, to reduce the size of the generated Monte Carlo ensemble by several orders of magnitude. Thus, the developed method allows faster simulations and makes it possible to solve the dynamics of the certain class of no…
Nonlinear effects in optical pumping of a cold and slow atomic beam
2015
By photoionizing hyperfine (HF) levels of the Cs state $6{\phantom{\rule{0.16em}{0ex}}}^{2}{P}_{3/2}$ in a slow and cold atom beam, we find how their population depends on the excitation laser power. The long time (around $180\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{s})$ spent by the slow atoms inside the resonant laser beam is large enough to enable exploration of a unique atom-light interaction regime heavily affected by time-dependent optical pumping. We demonstrate that, under such conditions, the onset of nonlinear effects in the population dynamics and optical pumping occurs at excitation laser intensities much smaller than the conventional respective saturation values. The ev…
Correction: Generalized Langevin dynamics: construction and numerical integration of non-Markovian particle-based models.
2018
Correction for ‘Generalized Langevin dynamics: construction and numerical integration of non-Markovian particle-based models’ by Gerhard Jung et al., Soft Matter, 2018, DOI: 10.1039/c8sm01817k.