17,132 research outputs found
Analytical solutions for the electric field and dielectrophoretic force in a dielectrophoretic focusing electrode structure
The analysis of the movement of particles in a nonuniform field requires accurate knowledge of theelectric field distribution. In this letter, the SchwarzâChristoffel mapping method is used to analytically solve the electric field distribution in a dielectrophoretic focusing electrode structure.The analytical result for the electric field distribution is validated by comparison with numericalsimulations using the finite element method. The electric field solution is used to calculate the dielectrophoretic force on a particle in the syste
Analytical and numerical modeling methods for impedance analysis of single cells on-chip
Electrical impedance spectroscopy (EIS) is a noninvasive method for characterizing the dielectric properties of biological particles. The technique can differentiate between cell types and provide information on cell properties through measurement of the permittivity and conductivity of the cell membrane and cytoplasm. In terms of lab-on-a-chip (LOC) technology, cells pass sequentially through the microfluidic channel at high speed and are analyzed individually, rather than as traditionally done on a mixture of particles in suspension. This paper describes the analytical and numerical modeling methods for EIS of single cell analysis in a microfluidic cytometer. The presented modeling methods include Maxwellâs mixture theory, equivalent circuit model and finite element method. The difference and advantages of these methods have been discussed. The modeling work has covered the static case â an immobilized cell in suspension and the dynamic case â a moving cell in the channel
ASCA observations of two SNRs and NEI analysis
Based on the data from the \asca observation of SNRs Kes79 and W49B, we
present here the analysis of their X-ray spectra and morphologies. The Kes79
spectrum can be well fitted by a single NEI component, and the narrow-band
images of that source show an inhomogeneous distribution of heavy elements. The
heavy elements are richest in the positions S, SE and SW of Kes79, where there
may exist interaction between shocks and molecular clouds implied by radio
observations. For W49B we present here the non-equilibrium ionization (NEI)
analysis based on its emission line diagnostics, and the spectral fit using two
NEI components. The reverse shock in W49B may be still hot and we don't find
evidence for a hotter blast wave in \asca spectra.Comment: Contributed talk in 32nd COSPAR E1.1, 1998, Nagoya. To appear in Adv.
Space Res., 1999, 6 pages, LaTe
A Sino-German 6\ cm polarization survey of the Galactic plane VI. Discovery of supernova remnants G178.2-4.2 and G25.1-2.3
Supernova remnants (SNRs) were often discovered in radio surveys of the
Galactic plane. Because of the surface-brightness limit of previous surveys,
more faint or confused SNRs await discovery. The Sino-German 6\ cm
Galactic plane survey is a sensitive survey with the potential to detect new
low surface-brightness SNRs. We want to identify new SNRs from the 6\
cm survey map of the Galactic plane. We searched for new shell-like objects in
the 6\ cm survey maps, and studied their radio emission, polarization,
and spectra using the 6\ cm maps together with the 11\ cm and
21\ cm Effelsberg observations. Extended polarized objects with
non-thermal spectra were identified as SNRs. We have discovered two new, large,
faint SNRs, G178.2-4.2 and G25.1-2.3, both of which show shell structure.
G178.2-4.2 has a size of 72 arcmin x 62 arcmin with strongly polarized emission
being detected along its northern shell. The spectrum of G178.2-4.2 is
non-thermal, with an integrated spectral index of . Its
surface brightness is , which makes G178.2-4.2 the second faintest known Galactic SNR.
G25.1-2.3 is revealed by its strong southern shell which has a size of 80
arcmin x 30\arcmin. It has a non-thermal radio spectrum with a spectral index
of . Two new large shell-type SNRs have been detected at
6\ cm in an area of 2200 deg^2 along the the Galactic plane. This
demonstrates that more large and faint SNRs exist, but are very difficult to
detect.Comment: 8 pages, 8 figures, accepted by Astronomy and Astrophysics. For the
version with high resolution figures, please go to
http://zmtt.bao.ac.cn/6cm/papers/2newSNR.pd
Simulation of the Aerodynamic Interaction between Rotor and Ground Obstacle Using Vortex Method
The mutual aerodynamic interaction between rotor wake and surrounding obstacles is complex, and generates high compensatory workload for pilots, degradation of the handling qualities, and performance, and unsteady force on the structure of the obstacles. The interaction also affects the minimum distance between rotorcrafts and obstacles to operate safely. A vortex-based approach is then employed to investigate the complex aerodynamic interaction between rotors and ground obstacle, and identify the distance where the interaction ends, and this is also the objective of the GARTEUR AG22 working group activities. In this approach, the aerodynamic loads of the rotor blades are described through a panel method, and the unsteady behaviour of the rotor wake is modelled using a vortex particle method. The effects of the ground plane and obstacle are accounted for via a viscous boundary model. The method is then applied to a âLargeâ and a âWeeâ rotor near the ground and obstacle, and compared with the earlier experiments carried out at the University of Glasgow. The results show that predicted rotor induced inflow and flow field compare reasonably well with the experiments. Furthermore, at certain conditions, the tip vortices are pushed up and re-injected into the rotor wake due to the effect of the obstacle resulting in a recirculation. Moreover, contrary to without the obstacle case, peak and thickness of the radial outwash near the obstacle are smaller due to the barrier effect of the obstacle, and an upwash is observed. In addition, as the rotor closes to the obstacle, the rotor slipstreams impinge directly on the obstacle, and the upwash near the obstacle is faster, indicating a stronger interaction between the rotor wake and the obstacle. In addition, contrary to the case without the obstacle, the fluctuations of the rotor thrust, and rolling and pitching moments are obviously strengthened. When the distance between the rotor and the obstacle is larger than 3R, the effect of the obstacle is small
Unsteady Aerodynamic Interaction Between Rotor and Ground Obstacle
The mutual aerodynamic interaction between rotor wake and surrounding obstacles is complex, and
generates high compensatory workload for pilots, degradation of the handling qualities and performance,
and unsteady force on the structure of the obstacles. The interaction also affects the minimum distance
between rotorcrafts and obstacles to operate safely. A vortex-based approach is then employed to
investigate the complex aerodynamic interaction between rotors and ground obstacle, and identify the
distance where the interaction ends, and this is also the objective of the GARTEUR AG22 working group
activities. In this approach, the aerodynamic loads of the rotor blades are described through a panel method,
and the unsteady behaviour of the rotor wake is modelled using a vortex particle method. The effects of the
ground plane and obstacle are accounted for via a viscous boundary model. The method is then applied to a
âLargeâ and a âWeeâ rotor near the ground and obstacle, and compared with the earlier experiments carried
out at the University of Glasgow. The results show that the predicted rotor induced inflow and flow field
compare reasonably well with the experiments. Furthermore, at certain conditions the tip vortices are pushed
up and re-injected into the rotor wake due to the effect of the obstacle resulting in a recirculation. Moreover,
contrary to without the obstacle case, the peak and thickness of the radial outwash near the obstacle is
smaller due to the barrier effect of the obstacle, and an up-wash is observed. Additionally, as the rotor closes
to the obstacle, the rotor slipstreams impinge directly on the obstacle, and the up-wash near the obstacle is
faster, indicating a stronger interaction between the rotor wake and the obstacle. Also, contrary to the case
without the obstacle, the fluctuations of the rotor thrust, rolling and pitching moments are obviously
strengthened. When the distance between the rotor and the obstacle is larger than 3R, the effect of the
obstacle is small
The evaluation of the rate constants for a reversible unimolecular hydrogen transfer reaction that involves a cyclic transition state
Intermolecular hydrogen transfer free radical reactions are common in the
combustion process and in a number of organic chemistry reactions. Therefore,
evaluating the pressure and temperature-dependent rate constants of them is of
great importance. Basing on microcanonical Rice-Ramsperger-Kassel-Marcus (RRKM)
theory, tunnelling correction, and internal rotation correction, we present a
simple model that is able to give an estimate of the desired rate constants of
a reversible unimolecular reaction. We then extend the simple reversible
reaction model to calculate the overall relaxation rate constants of the
combustion process of propane
Parking and the visual perception of space
Using measured data we demonstrate that there is an amazing correspondence
among the statistical properties of spacings between parked cars and the
distances between birds perching on a power line. We show that this observation
is easily explained by the fact that birds and human use the same mechanism of
distance estimation. We give a simple mathematical model of this phenomenon and
prove its validity using measured data
D-Instanton in AdS_5 and Instanton in SYM_4
Following the observation of Banks and Green that the D-instantons in AdS_5
correspond to the instantons in 4-dimensional supersymmetric Yang-Mills theory,
we study in more detail this correspondence for individual instantons. The
supergravity solution for a D-instanton in AdS_5 is found using the ansatz used
previously for D-instantons in flat space. We check that the actions and
supersymmetries match between the D-instanton solution and the Yang-Mills
instanton. Generalizing this result, we propose that any supergravity solution
satisfying the ansatz corresponds to a (anti-)self-dual Yang-Mills
configuration. Using this ansatz a family of identities for correlation
functions in the supersymmetric Yang-Mills theory are derived.Comment: LaTeX, 19 pages, no figure, some typos correcte
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