Search results for "Radial distribution"
showing 10 items of 40 documents
Optimal calculation of the pair correlation function for an orthorhombic system
2012
We present a new computational method to calculate arbitrary pair correlation functions of an orthorombic system in the most efficient way. The algorithm is demonstrated by the calculation of the radial distribution function of shock compressed liquid hydrogen.
An improved method for determining voltage collapse proximity of radial distribution networks
2005
The two-bus equivalent model is commonly used for voltage stability studies in both distribution and transmission systems. The paper presents a simple method to evaluate, for each bus, the parameters which define the equivalent circuit of a radial distribution network. In particular, a straightforward way for determining the Thévenin equivalent impedance behind a load node is proposed, which allows to better identify the maximum loading point beyond which the voltage collapse takes place in the network. Simulation results show that the proposed method is significantly more accurate than other existing methods on evaluating the critical power at a particular node (i.e. the weak node of the n…
Heterogeneity at the glass transition: a review
1999
Theoretical concepts and experimental evidence of heterogeneity in glass-forming liquids and polymers are reviewed. The main purpose is to provide an introduction to theoretical developments and recent experiments which have led to rapidly increasing knowledge. Realizing that there is no consensus in regard to the various scenarios of the glass transition starting from rather different assumptions we try to give a balanced overview although we also compare and interrelate some of the approaches. The experimental part describes recent nuclear magnetic resonance, dielectric, and optical experiments from which dynamically distinguishable subensembles can be selected thus proving the existence …
A new backward/forward method for solving radial distribution networks with PV nodes
2008
Abstract In this paper, a new backward/forward (b/f) methodology for the analysis of distribution systems with constant power loads is presented. In the proposed method, at each iteration, the loads are considered as constant impedances; in the backward sweep all the network variables (bus voltages and branch currents) are evaluated considering a scaling factor which is determined at the end of the backward phase. Indeed the forward sweep is eliminated and the node voltages calculation does not demand the sequentiality needed in the b/f methodology. The developed method, although deriving conceptually from the b/f methodology, presents only the backward phase in which all the network variab…
Structure and Dynamics of NaCl in Methanol. A Molecular Dynamics Study
1991
Abstract A recently developed flexible three-site model for methanol was employed to perform a Molecular Dynamics simulation of a 0.6 molal NaCl solution. The ion-methanol and ion-ion potential functions were derived from ab initio calculations. The structural properties of the solution are discussed on the basis of radial and angular distribution functions, the orientation of the methanol molecules, and their geometrical arrangement in the solvation shells of the ions. The dynamical properties of the solution - like self-diffusion coefficients, hindered translations, librations, and internal vibrations of the methanol molecules - are calculated from various autocorrelation functions.
Investigating the cooling rate dependence of amorphous silica: A computer simulation study
1996
We use molecular dynamics computer simulations to study the dependence of the properties of amorphous silica on the cooling rate with which the glass has been produced. In particular we show that the density, the glass transition temperature, the radial distribution function and the distribution of the size of the rings depend on the cooling rate.
Structure of natural water-containing glasses from Lipari (Italy) and Eastern Rhodopes (Bulgaria): SAXS, WAXS and IR studies
1998
Abstract Two natural water-containing glasses with rhyolite composition originating from two different areas (perlite from Lipari, Italy, and expanded perlite from the Eastern Rhodopes, Bulgaria) have been characterised for chemical composition, atomic structure and specific surface area, with the ultimate goal of exploitation of volcanic glasses as carriers for heterogeneous metal catalysts. The two samples have similar chemical composition and total water content. The local structure, as determined by radial distribution function analysis of the wide angle X-ray scattering patterns, is similar, the medium-range structure being slightly more ordered for the Lipari glass. These results are …
Fine-Scale Droplet Clustering in Atmospheric Clouds: 3D Radial Distribution Function from Airborne Digital Holography
2018
The extent of droplet clustering in turbulent clouds has remained largely unquantified, and yet is of possible relevance to precipitation formation and radiative transfer. To that end, data gathered by an airborne holographic instrument are used to explore the three-dimensional spatial statistics of cloud droplet positions in homogeneous stratiform boundary-layer clouds. The three-dimensional radial distribution functions g(r) reveal unambiguous evidence of droplet clustering. Three key theoretical predictions are observed: the existence of positive correlations, onset of correlation in the turbulence dissipation range, and monotonic increase of g(r) with decreasing r. This implies that cur…
Iterative integral equation methods for structural coarse-graining
2021
In this paper, new Newton and Gauss-Newton methods for iterative coarse-graining based on integral equation theory are evaluated and extended. In these methods, the potential update is calculated from the current and target radial distribution function, similar to iterative Boltzmann inversion, but gives a potential update of quality comparable with inverse Monte Carlo. This works well for the coarse-graining of molecules to single beads, which we demonstrate for water. We also extend the methods to systems that include coarse-grained bonded interactions and examine their convergence behavior. Finally, using the Gauss-Newton method with constraints, we derive a model for single bead methano…
Load Flow Solution of radial distribution networks with ZI loads
2008
In this paper, a methodology to solve radial distribution networks, with constant current and/or impedance loads, is proposed. The techniques currently available to solve such systems are based either on iterative methods or on the bus impedance matrix. The method developed is the extension of a technique that is valid to solve networks made of impedances with one supply point. The methodology can be applied to directly and rapidly solve large distribution systems in which the loads are modeled as constant current/impedance. It is also able to solve meshed systems having voltage-dependent loads, inside an iterative backward/forward method.