364,257 research outputs found
Application of the Waveform Relaxation Technique to the Co-Simulation of Power Converter Controller and Electrical Circuit Models
In this paper we present the co-simulation of a PID class power converter
controller and an electrical circuit by means of the waveform relaxation
technique. The simulation of the controller model is characterized by a
fixed-time stepping scheme reflecting its digital implementation, whereas a
circuit simulation usually employs an adaptive time stepping scheme in order to
account for a wide range of time constants within the circuit model. In order
to maintain the characteristic of both models as well as to facilitate model
replacement, we treat them separately by means of input/output relations and
propose an application of a waveform relaxation algorithm. Furthermore, the
maximum and minimum number of iterations of the proposed algorithm are
mathematically analyzed. The concept of controller/circuit coupling is
illustrated by an example of the co-simulation of a PI power converter
controller and a model of the main dipole circuit of the Large Hadron Collider
Parametric Macromodels of Drivers for SSN Simulations
This paper addresses the modeling of output and power supply ports of digital drivers for accurate and efficient SSN simulations. The proposed macromodels are defined by parametric relations, whose parameters are estimated from measured or simulated port transient responses, and are implemented as SPICE subcircuits. The modeling technique is applied to commercial high-speed devices and a realistic simulation example is shown
WILL COUNTRY-OF-ORIGIN LABELING (COOL) BE 'COOL' FOR THE U.S. MEAT INDUSTRY?
The study develops a Muth-type equilibrium displacement model that is able to estimate impacts of COOL on multistage beef production system and its trade relations. The model includes equilibrium conditions of each production stage with consideration of trade and market structure. A unique feature of this model is that it allows for retailer's oligopsony power separately from processor's market power. Simulation results indicate that the cost of COOL would outweigh the overall industry benefit unless COOL leads to low cost increases and more than a 10% increase in consumers' willingness to pay. The COOL provision is expected to have relatively smaller negative impact on cow-calf producers, backgrounders, and feedlots than on packers and retailers.International Relations/Trade,
Recent Developments in Cointegration
It is well known that inference on the cointegrating relations in a vector autoregression
(CVAR) is difficult in the presence of a near unit root. The test for a given cointegration vector can have
rejection probabilities under the null, which vary from the nominal size to more than 90%. This paper
formulates a CVAR model allowing for multiple near unit roots and analyses the asymptotic
properties of the Gaussian maximum likelihood estimator. Then two critical value adjustments
suggested by McCloskey (2017) for the test on the cointegrating relations are implemented for the
model with a single near unit root, and it is found by simulation that they eliminate the serious size
distortions, with a reasonable power for moderate values of the near unit root parameter. The findings
are illustrated with an analysis of a number of different bivariate DGPs
Behaviour of microscale gas flows based on a power-law free path distribution function
We investigate a power-law form for the probability distribution function of free paths of dilute gas molecules in a confined region. A geometry-dependent effective molecular mean free path (MFP) model is then derived for a planar wall confinement, by taking into account the boundary limiting effects on the molecular paths. The power-law based effective MFP is validated against molecular dynamics simulation data and compared with exponential effective MFP models. The Navier-Stokes constitutive relations are then modified according to the kinetic theory of gases i.e. transport properties can be described in terms of the free paths which the molecules describe between collisions. Results for isothermal pressure-driven Poiseuille gas flows in micro-channels are reported, and we compare results with conventional hydrodynamic models, solutions of the Boltzmann equation and experimental data
A Note on Power-Laws of Internet Topology
The three Power-Laws proposed by Faloutsos et al(1999) are important
discoveries among many recent works on finding hidden rules in the seemingly
chaotic Internet topology. In this note, we want to point out that the first
two laws discovered by Faloutsos et al(1999, hereafter, {\it Faloutsos' Power
Laws}) are in fact equivalent. That is, as long as any one of them is true, the
other can be derived from it, and {\it vice versa}. Although these two laws are
equivalent, they provide different ways to measure the exponents of their
corresponding power law relations. We also show that these two measures will
give equivalent results, but with different error bars. We argue that for nodes
of not very large out-degree( in our simulation), the first Faloutsos'
Power Law is superior to the second one in giving a better estimate of the
exponent, while for nodes of very large out-degree() the power law
relation may not be present, at least for the relation between the frequency of
out-degree and node out-degree.Comment: 16 pages, 3 figure
A review of wildland fire spread modelling, 1990-present 2: Empirical and quasi-empirical models
In recent years, advances in computational power and spatial data analysis
(GIS, remote sensing, etc) have led to an increase in attempts to model the
spread and behaviour of wildland fires across the landscape. This series of
review papers endeavours to critically and comprehensively review all types of
surface fire spread models developed since 1990. This paper reviews models of
an empirical or quasi-empirical nature. These models are based solely on the
statistical analysis of experimentally obtained data with or without some
physical framework for the basis of the relations. Other papers in the series
review models of a physical or quasi-physical nature, and mathematical
analogues and simulation models. The main relations of empirical models are
that of wind speed and fuel moisture content with rate of forward spread.
Comparisons are made of the different functional relationships selected by
various authors for these variables.Comment: 22 pages + 7 pages references + 2 pages tables + 2 pages figures.
Submitted to International Journal of Wildland Fir
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