28,810 research outputs found
On the mechanical behaviour of thin perforated plates and their application in silicon condenser microphones
In this paper an alternative approach to the modelling of plates with a large number of holes is presented. By means of plate theory, it is shown that perforated plates can be modelled by conventional orthotropic plates with modified elastic properties. The modification of the elastic constants is derived by equalizing the strain-energy of the perforated and the orthotropic plate. The model obtained is then compared with previous methods and applied in the electrochemical simulation of a silicon micromachined microphone structure. The microphone structures are simulated numerically, using an algorithm based on finite differences
Fitting Effective Diffusion Models to Data Associated with a "Glassy Potential": Estimation, Classical Inference Procedures and Some Heuristics
A variety of researchers have successfully obtained the parameters of low
dimensional diffusion models using the data that comes out of atomistic
simulations. This naturally raises a variety of questions about efficient
estimation, goodness-of-fit tests, and confidence interval estimation. The
first part of this article uses maximum likelihood estimation to obtain the
parameters of a diffusion model from a scalar time series. I address numerical
issues associated with attempting to realize asymptotic statistics results with
moderate sample sizes in the presence of exact and approximated transition
densities. Approximate transition densities are used because the analytic
solution of a transition density associated with a parametric diffusion model
is often unknown.I am primarily interested in how well the deterministic
transition density expansions of Ait-Sahalia capture the curvature of the
transition density in (idealized) situations that occur when one carries out
simulations in the presence of a "glassy" interaction potential. Accurate
approximation of the curvature of the transition density is desirable because
it can be used to quantify the goodness-of-fit of the model and to calculate
asymptotic confidence intervals of the estimated parameters. The second part of
this paper contributes a heuristic estimation technique for approximating a
nonlinear diffusion model. A "global" nonlinear model is obtained by taking a
batch of time series and applying simple local models to portions of the data.
I demonstrate the technique on a diffusion model with a known transition
density and on data generated by the Stochastic Simulation Algorithm.Comment: 30 pages 10 figures Submitted to SIAM MMS (typos removed and slightly
shortened
An IC-compatible polyimide pressure sensor with capacitive readout
A capacitive differential pressure sensor has been developed. The process used for the fabrication of the sensor is IC-compatible, meaning that the device potentially can be integrated on one chip with a suitable signal-conditioning circuit. A sensor for a differential pressure of ±1 bar has been fabricated and tested with a frequency-modulated detection circuit, and good agreement is found with the theoretical model of the sensor. A nominal sensitivity ¿C/C of 17% has been measured for a positive differential pressure of 1 bar. The resolution of the complete detection system is 2.5 mbar (250 Pa)
Crystallization of the Wahnstr\"om Binary Lennard-Jones Liquid
We report observation of crystallization of the glass-forming binary
Lennard-Jones liquid first used by Wahnstr\"om [G. Wahnstr\"om, Phys. Rev. A
44, 3752 (1991)]. Molecular dynamics simulations of the metastable liquid on a
timescale of microseconds were performed. The liquid crystallized
spontaneously. The crystal structure was identified as MgZn_2. Formation of
transient crystallites is observed in the liquid. The crystallization is
investigate at different temperatures and compositions. At high temperature the
rate of crystallite formation is the limiting factor, while at low temperature
the limiting factor is growth rate. The melting temperature of the crystal is
estimated to be T_m=0.93 at rho=0.82. The maximum crystallization rate of the
A_2B composition is T=0.60+/-0.02.Comment: 4 pages, 4 figures; corrected typo
Organic field-testing of compounds to control apple scab (Venturia inaequalis) in combination with alleyway cover crops
To find new potential fungicides acceptable to organic production preventing apple scab (Venturia inaequalis) infections on leaf and fruits during primary apple scab infection period.
The trials were carried out in combination with different cover crop treatments in single-tree plots. The formerly resistant variety ‘Delorina’ on rootstock M9, planted 1995 at a planting distance of 3.3 m x 1.6 m, unfertilized and with mechanical weed cleaning in the tree row, were used. The experimental orchard is located at Research Centre Aarslev (100 27´ E, 550 18´N)
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