Proceedings of the Electrostatics Society of America
June 23 - 25, 1999
Boston University
Boston, Massachusetts
A bound copy of these Proceedings in their entirely can be obtained from Laplacian Press:
Contents
Charges and Fields
Corona Current in a Wire Cylinder System Revisited by James Q. Feng
Dual Trichel like Emission from Unipolar Corona Points — A Basic DC
to AC Conversion
Mechanism by T.S. Lee
Radar Diagnoses of Atmospheric Electricity by M. C. Lee and J. Jastrzebski
Comparative Study of Theoretical Kerr Electro Optic Fringe Patterns
in Two Dimensional and
Axisymmetric Electrode Geometries by A. Ustundag and M. Zahn
Electrostatic Aspects of Helicity in Space Physics by P. Robert Kotiuga
Powders and Particles
The Effect of Fluidizing and Transport Air Relative Humidity on Corona
and Tribocharging in
the Powder Painting Process by R. A. Sims and M. K. Mazumder
A Method to Determine the Surface Charge Density of a Powder Having
an Arbitrary Particle
Size Distribution by Albert E. Seaver
Bipolar Charging Effects in Polydisperse Powders by F. S. Ali, G.
S. P. Castle, 1.1. Inculet
and H. Zhao
Electrophoretic and Dielectrophoretic Particle Control and Transport
with a New Separation
Apparatus by Jack Macknis
Surface Charge Distribution Analysis by Fluorescent Microsphere Imaging
Technique by M. K.
Mazumder, K. Tennal, and D. Lindquist
EHD Atomization of Ceramic Suspensions by W. Balachandran
Sensors and Measurements
Applications of Quasistatic Sensors: From Cure Monitoring to Landmine
Imaging and Detection
by Andrew Washabaugh, Yanko Sheiretov, Darrell Schlicker, and Neil
Goldfine
Measurements of Moisture Diffusion Dynamics in Transformer Insulation
Using Interdigital
Dielectrometry Measurements by Y. Du, S. H. Kang, A. V. Mamishev,
B. C. Lesieutre, and
M. Zahn
Forward and Inverse Parameter Estimation Algorithms of Interdigital
Dielectrometry Sensors by
B.C. Lesieutre, A. V. Mamishev, Y. Du, E. Keskiner,G.C. Verghese,
and M. Zahn
Applied Electrostatics
Ion Beam Contouring to Generate Sub Millimeter Optics by Thomas
G. Bifano, Mark N.
Horenstein, Mike Feinberg, and Prahsant Shanbhag
A Micro Scale Electric Induction Machine for a Micro Gas Turbine Generator
by
Steven F.
Nagle and Jefferey H. Lang
Production of Ions and Nanoparticles from Taylor Cone Jets Of
Highly Conducting Organic
Electrolytes by J. Fernandez de la Mora and M. Gamero Castano
Control of Foodborne Pathogenic Microorganisms Using Electric Discharge
Generated Ozone
Enhanced by Ultraviolet Photons by S. Edward Law and Michael E.
Diaz
Lumped Element Model for Computing the Equilibrium Charge Distribution
Along a Moving
Web by Mark N. Horenstein
Relating Roller Shaft Voltages to Tribocharging During Sheet Transport
by
Humphrey Wong
Dielectrics and Materials
The Effects of Electric Field Radiated from Electrostatic Discharge
on the Electronic Circuit by
Jiu Sheng Huang
A Theoretical Paradox Related to Solid Dielectrics that Cannot be Resolved
even after a
Computer Simulation Using Finite Element Analysis by Andreas Trupp
Piezoelectric Effect on Ice by Hasashi Shio
A New Unifed Method for Measurement of Electrical Resistivity of Textile
Assemblies by
Pellumb G. Berberi
A Method to Estimate the Area of Contact of a Textile Fabric with a
Rigid Flat Surface by
Pellumb G. Berberi, J. Amirbayat, L. Porat
At the dawn of the Industrial Revolution, electrostatics was an emerging
branch of scientific
discovery. Given what we know today about electrostatics, it's hard
to imagine the sense of
mystery and wonder that must have confronted early experimenters such
as Franklin, Kelvin,
Coulomb, Faraday, Cavendish, and others. Through basic observation
and deductive reasoning,
these scientists developed a deep understanding of electrostatics,
paving the way for the
mathematical explanations recounted in Maxwell's Treatise on Electricity
and Magnetism.
Although electrostatics retains its status as one of the oldest branches
of physics, it continues to
this day to be a vibrant and ever emerging field of study that touches
our lives on a daily basis.
We've come to accept copy machines, laser printers, fax machines, flat
panel displays,
microphones, high speed printing, digital cameras, and airbag sensors—all
electrostatic
devices— as part of everyday life. Although modern electrostatics has
its roots in the same
fundamentals discovered by the early experimenters, it has been transformed
into an engineering
discipline with strong ties to industry and commercial applications.
In the spirit of modern electrostatics, the papers contained in these
proceedings reflect a great
diversity of state of the art topics in science and engineering. Indeed,
individuals from other
fields may marvel at the wide range of ideas that fall within the domain
of electrostatics. These
proceedings include papers on the use of electrostatics in imaging
systems, coating processes,
atmospheric probing, micro electromechanical systems, land mine detection,
industrial sensors,
biological pathogen control, and nanoscale particle production. Also,
while much of
electrostatics deals with the harnessing of electrostatic charge, a
large part of the discipline deals
with eliminating its effects. Several of topics in these proceedings,
including papers on
electrostatic discharge (ESD), charge neutralization, and web charging,
address this alternative
perspective.
This sixth printing of the ESA Conference Proceedings continues a tradition
that started in
1994 with the help of Laplacian Press and Electrostatic Applications.
Initially, ESA meetings
consisted of oral presentations only, and no permanent record of the
many interesting talks and
presentations was available. Since its inception, the annual ESA Proceedings
has become an
oft cited part of the vast body of literature in electrostatics. It
also has provided a means for
conveying the content of the annual meeting to those individuals unable
to attend. Besides
providing a permanent record of the conference, these proceedings are
meant to encourage
further discussions and interactions among the attendees, ESA members,
and members of our
counterpart organizations in the United States and in other countries.
May the spirit of the ESA,
known by all as "The Friendly Society," continue to permeate our meetings,
proceedings, social
events, and technical discussions. On behalf of the Department of Electrical
and Computer
Engineering at Boston University, it is with great pleasure that I
welcome you to the 1999
Annual ESA Conference.
For the Friendly Society,
Mark N. Horenstein
1999 Conference Chair
Corona Current in a Wire Cylinder System Revisited
James Q. Feng
Xerox Corporarion
800 Phillips Road, Webster, NY 14580, USA
Corona current can be generated in air or in other kinds of gas media
from a thin wire enclosed
in a concentric cylinder, when the voltage difference applied between
the wire and the cylinder
exceeds a threshold value. The threshold voltage difference for corona
onset corresponds to the
local electric field strength around the wire becoming aufficiently
large to cause localized air
breakdown or, in other words, to ionize some of the gas molecules.
In the case of positive
corona, i. e., the electric field is directed outward from the wire,
so that negative ions in the
ionization zone are drawn toward the wire whereas positive ions drift
along the electric field lines
toward the cylinder. A unipolar charge current is established in the
drift zone where ions of one
sign are dominant and those charge carriers are set in motion in response
to the electric field.
Although a wire cylinder system represents one of a few simplest system
configurations for
corona current generation, some commonly used theoretical formulas
in the literature have
lacked rigorous mathematical derivation and analysis [ 1]. In the present
work, a quadratic form
of the relationship between corona current and applied voltage is shown
to be a very reasonable
approximation to the complicated exact result. However, the form of
the coefficient in the
present quadratic formula is quite different from that of Townsend's
quadratic formula for small
current [ 1 2]. Experimental data are gathered to compare with the
theory.
Radar Diagnoses of Atmospheric Electricity
M. C. Lee and J. Jastrzebski
Department of Electrical and Computer Engineering
Boston University
Boston, Massachusetts 02215
Ph: 617 353 3363, e mail: mclee@enga.bu.edu
In this paper we discuss two phenomena of atmospheric electricity diagnosed
by radars.
They are (1) energetic electrons precipitated from radiation belts,
and (2) dense and hot
electrons induced by lightning. High energy electrons are trapped by
Earth's magnetic field in the
radiation belts. However, whistler waves can interact resonantly with
these electrons and
change their pitch angles. As the electrons fall in the loss cone of
the Earth's magnetic field, they
move freely and precipitate into the lower atmosphere, causing layers
of anomalous ionization.
Controlled study of precipitated electrons from radiation belts was
conducted at Arecibo, using
injected VLF waves from the ground. After the ionosphere is heated
by high power O mode
HF waves, large scale density irregularity sheets are generated and
aligned in parallel with the
meridional plane, forming multi parallel plate waveguides (viz., ionospheric
ducts) for ducted
radio wave propagation. VLF waves injected from the ground based transmitter,
impinge at the
boundary between the neutral atmosphere and the disturbed ionosphere,
and effectively couple
into the ionospheric ducts. When the VLF waves enter the ionosphere,
they change from linear
into circular polarization and propagate in the form of whistler waves.
These ducted whistler
waves were recorded at the magnetic conjugate point, Trelew, Argentina
by a VLF receiver.
Triggered particle precipitation events were monitored by a UHF incoherent
radar over
Arecibo. Our results show that electrons with energy exceeding 100
eV can be precipitated into
the atmosphere at the o0 80 km altitudes to produce thin but dense
ionization layers, giving rise
to intense radar backscatter echoes.
We used S band, C band, and UHF radars to investigate the reflectivity
of lightning induced
plasmas, by means of radio wave scattering from electron density fluctuations.
The lightning
induced hot and dense electrons are modelled as long, perfectly conducting
cylinders with
surface density fluctuations on a scale much smaller than the total
channel length. The theoretical
wavelength dependence of the radar reflectivity is compared with experimental
results. It is
found that the theory of rough surface scattering predicts two types
of inverse power law
wavelength dependence for radar reflectivity. They are inversely proportional
to the wavelength
and the squared wavelength, which correspond to density fluctuations
of lightning plasmas with
a Gaussian type spectrum and a power law type spectrum, respectively.
By contrast, the theory
of long, thin conductors predicts a square root of wavelength dependence
for radar reflectivity.
The experimental observations on common lightning targets free of precipitation
masking effects
show a mean wavelength dependence Iying between the predictions of
the two theories. It
means that the wavelength dependence in these observations is bounded
by these two theories.
We conclude that the theory for the overdense plasma channels with
irregular surfaces and the
theory for long, thin overdense channels bracket the observed wavelength
dependence.
Comparative Study of TheoreticalKerr Electro Optic Fringe
Patterns in Two Dimensional and Axisymmetric Electrode
Geometries
A. Ustundag and M. Zahn
Department of Electrical Engineering and Computer Science
Laboratory for Electromagnetic and Electronic Systems
Massachusetts Institute of Technology
Cambridge, MA 02139
Kerr electro optic fringe patterns have long been used to study space
charge injection and
transport phenomena in highly birefringent materials such as nitrobenzene.
The past experimental
work has been limited to one or two dimensional geometries where the
electric field magnitude
and direction have been constant along the light path such as two concentric
or parallel cylinders
or parallel plate electrodes. For these geometries the light maxima
and minima in the fringe
patterns can directly be used to find the electric field magnitude
and direction.
In this work we calculate theoretical Kerr electro optic fringe patterns
for an axisymmetric
point/plane electrode geometry for which the electric field magnitude
and direction vary along
the light path. We compare these patterns to the fringe patterns of
the two dimensional analog,
blade/plane geometry. We underline the differences and study how these
fringe patterns can be
used to reconstruct the axisymmetric electric field components in practice.
It is of interest to
extend the Kerr electro optic measurement technique to point/plane
electrode geometry which
is often used in high voltage research to create large electric fields
for charge injection at known
location and at reasonable voltages.
Electrostatic Aspects of Helicity in Space Physics
P. Robert Kotiuga
Dept. of Electrical and Computer Engineering
Boston University
In recent decades, magnetic helicity has been identified as a conserved
quantity in many
plasmas governed by the equations of magnetohydrodynamics [l]. In particular,
many plasmas
relax to a state of minimal energy subject to the constraint that helicity
is conserved. This talk
begins by introducing all relevant concepts and illustrates them in
the context of space plasmas.
Magnetic helicity is a topological quantity and not like a conventional
conserved quantity
such as energy. For example, it changes sign if one considers a "mirror
image" problem. For this
reason, it is of great interest to compute its time rate of change
in nonideal plasmas and develop
a physical understanding of the result. This leads to the notion of
current helicity and other
"electrostatic terms". The purpose of this talk is to identify and
give meaning to these
electrostatic terms
.
[1] Invited talks from the Chapmann Conference on "Magnetic
Helicity in Space and
Laboratory Plasmas" held in Boulder Colorado, July 28
31, 1998, will soon appear as an
American Geophysical Union (AGU) monograph.
The Effect of Fluidizing and Transport Air Relative Humidity
on
Corona and Tribocharging in the Powder Painting Process
R. A. Sims and M. K. Mazumder
University of Arkansas at Little Rock
Department of Applied Science
ETAS 575, 2801 S. University
Little Rock, AR 72204
Tel: 501 569 8045, Fax: 501 569 8020
E mail: sims@eivax.ualr.edu
This paper presents the results from experimental studies of the effect
of the relative
humidity of the fluidization and transport air on the charging ability
of powder paint. These
studies measured the charge to mass ratio of acrylic automotive clear
coat powders and
industrial powder paint as the moisture content of the air used for
fluidization and transport was
varied from 0 •F to 35 •F dewpoint. Both corona and tribo charging
were studied.
A Method to Determine the Surface Charge Density of a
Powder
Having an Arbitrary Particle Size Distribution
Albert E. Seaver
3M Engineering Systems Technology Center
3M Center Bldg. 518 1 01
St. Paul, MN 55144 1000
Ph: (651) 733 8629 email: aeseaver@mmm. com
For safety reasons it is usually desirable to keep the charge on a powder
low during
transport and storage. On the other hand it is desirable to obtain
a very high charge on a
powder to be used in an electrostatic powder coating process. The surface
charge density rTs
on a particle will have an equilibrium value determined by its collisions
within its environment,
but this surface charge density can not exceed the Gaussian limit.
As a result, the charge on a
powder relative to the Gaussian limit can be used to describe the state
of the powder provided
the surface charge density of the powder can be estimated. Although
it is relatively easy to
measure the net charge Q and net mass M of a powder sample there is
no known method to
relate these measurements to the surface charge density as on the individual
particles in the
powder sample if the sample has a particle size distribution. This
paper examines the
mathematical relationship between Q, M and as and the results show
that the surface charge
density can be determined if a separate measurement of the particle
size distribution is also
made. To demonstrate the application of the analysis developed in this
paper the theory is
applied to the recent charge measurements on biological particulates
discussed by Banerjee and
Law.
Electrophoretic and Dielectrophoretic Particle Control
and Transport with a New Separation Apparatus
Jack Macknis
Lift Feeder, Inc.
Yardley, PA
Phone: 215 321 4776
Fax: 215 321 7003
Principles and applications will be presented for a new separator which
diverts selected
components of a fluid stream out of the main stream using electric
force fields (electrophoretic
or dielectrophoretic). In operation, a fluid stream is propelled axially
through a three dimensional array of field
gradients produced by a repetitive pattern of rods arranged at an angle
between parallel and
perpendicular to the initial flow direction into the separator. Those
materials which are attracted
or repulsed by electric field forces will move toward the outside walls
of the separator because
of the resultant force on them due to the combination of the force
propelling them axially through
the separator and the force fields set up inside the separator.
The fluid flows axially through the separator, with the wires or rods
disposed within the flow
volume and oriented at a given angle between parallel and perpendicular
to the direction of flow
of the fluid stream. The given angle is designed based on the relative
magnitude of the force
propelling the fluid stream axially through the separator and the forces
on the selected materials
due to the electric field forces between the plurality of small diameter
rods. The combination of
those forces and the angle of the rods produces resultant forces on
those select molecules or
particles sensitive to the field gradients,
which are different in relation to the particle or molecules location
relative to the rods.
When the field gradient force has a component opposite in direction
to the propelling force,
the resultant force moves the particle towards the outside wall, and
also within a channel formed
by the electric forces and parallel to the rods, because the angle
of the rods is the same as the
angle of the resultant force. These particles tend to maintain the
same relation relative to the
rods, and remain in the channel moving towards the outside wall. When
the field gradient force
has a component in the same direction as the propelling force, the
resultant force moves the
particle to a location where the field gradient has a component opposite
in direction to the
propelling force or the first case.
Thus, the select molecules or particles will concentrate in the channels
parallel to the rods
where the resultant force is towards the outside wall. At the outside
walls, partitions or slits to
an outer plenum are located to divert the flow into separate plenum
streams, where the select
molecules or particles are removed from the main fluid stream.
Advantages with this process include:
1) It is continuous with minimal contact and build up on the electrodes. The channels areSensors and Measurements
formed by the force fields with no physical hardware in the flow stream.
2) A highly effective separation volume. Effect is cumulative along the length. Each volume
passes through multiple capture sites.
3) Adaptable to a wide range of particles and molecules. Electric forces are produced
between multiple parallel rods which can be varied in diameter and spacing to produce a wide
range of gradient strength and size. This allows the process to be adaptable to a wide range of
particle sizes.
4) Moves the particles outside the main flow to a separate plenum so certain problems can
be worked on without interrupting the process.
5) Economically adaptable to nanoscale dimensions. Deposition on substrates possible.
6) Low energy and low pressure drop.
Applications of Quasistatic Sensors: From Cure Monitoring
to
Landmine Imaging and Detection
Andrew Washabaugh, Yanko Sheiretov, Darrell Schlicker, and Neil Goldfine
JENTEK Sensors, Inc.
200 Dexter Ave.
Watertown MA 02472
Phone: (617) 926 8422 Fax: (617) 926 8744
email: jentek@shore.net
Electromagnetic sensors that operate in the low frequency, quasistatic
regime are well suited
to materials characterization and defect monitoring applications. In
this regime the electric and
magnetic fields are decoupled and the sensor choice depends upon the
properties of the
materials being tested. For electroquasistatic (EQS) applications,
capacitive sensing
dielectrometry provides information for low conductivity materials,
such as layer thickness,
porosity, thermal conductivity, cure state, or the presence of defects,
through measurements of
the material electrical properties such as dielectric constant, conductivity,
loss tangent, or
complex permittivity. For magnetoquasistatic (MQS) applications, inductive
sensing
magnetometry provides information for high conductivity and magnetic
materials, such as layer
thickness, fatigue state, shot peen intensity, and crack size, through
measurements of material
properties such as magnetic susceptibility, electrical conductivity,
or complex permeability.
This paper focuses on dielectrometry applications and will describe
sensor configurations
and inversion methods for obtaining real time property estimates. Representative
applications to
be described include monitoring of epoxies during the curing transient,
dielectric coating
thickness measurement, monitoring of moisture concentrations in porous
transformer
pressboard insulation, detection of cracks in composite materials,
and imaging and detection
of nonmetal and metal objects such as landmines.
The capacitive sensors to be described are designed to provide measurements
on a single
side of a material. Electrodes are located in a single plane so that
the fringing electric fields
couple to the test material. In one implementation, the electrodes
consist of spatially periodic
interdigitated drive and sense electrodes. Since the electric field
satisfies Laplace's equation, the
spatial periodicity of the electrode structure or wavelength controls
the penetration depth of the
field into the test material and it is possible to generate a profile
of the material properties as a
function of depth at a given input frequency. This can be realized
with multiple sets of such
interdigitated structures by varying the spatial periodicity of the
electrode structure or with novel
electrode structures that provide multiple spatial wavelengths over
a fixed sensor footprint. This
approach allows for spatial profile measurements of dispersive media,
where the electrical
properties vary with the excitation field frequency and intensity.
AISO, arrays of capacitive
sensors can provide quantitative two dimensional imaging of low conductivity
materials.
The grid measurement methods to be described provide a real time solution
to the inverse
problem relating the material properties to the sensor impedance. These
grid measurement
methods use a database of sensor responses to map the measured signals
into the desired
properties for the material. The database is derived, prior to the
data acquisition, using a
'forward model' of the sensor response based on either a continuum
model or a finite element
model for the sensor and the specific problem of interest. The measurement
grids can be
visualized as grids that relate measured parameters, such as the magnitude
and phase of the
impedance, to the unknown parameters, such as the permittivity and
thickness of a dielectric
layer.
Measurements of Moisture Diffusion Dynamics in Transformer
Insulation Using
Interdigital Dielectrometry Measurements
Y. Du, S. H. Kang, A. V. Mamishev, B. C. Lesieutre, and M. Zahn
Massachusetts Institute of Technology
Cambridge, MA 02139
The moisture diffusion process in oil free transformer pressboard is
monitored using an
interdigital dielectrometry three wavelength sensor in a specially
constructed bench top
apparatus. Experiments are performed for five different temperatures
at various moisture levels.
The time evolution of the moisture spatial profile in transformer pressboard
is non destructively
estimated. Experimental results have a good agreement with theoretical
analysis of the moisture
diffusion equation on the effects of pressboard thickness and temperature
on the diffusion
process.
The diffusion coefficient for oil free pressboard as a function of temperature
and moisture
concentration is estimated. Numerical methods of solving the non linear
diffusion equation are
developed. Literature results of the diffusion coefficient for cellulose
insulation are compared
and analyzed.
The interdigital sensor setup is also combined in a transformer oil
Couette Facility that
simulates the transformer environment for studying temperature and
moisture transients in
pressboard. The understanding of moisture related processes in power
transformers can be
enhanced with this methodology.
Forward and Inverse Parameter Estimation Algorithms of Interdigital Dielectrometry Sensors
B.C. Lesieutre, A.V. Mamishev, Y. Du, E. Keskiner,
G.C. Verghese, and M. Zahn
Massachusetts Institute of Technology
Cambridge, MA 02139
In this paper we extend the continuum model for interdigital dielectrometry
sensors and
propose a new, direct technique for estimating material electrical
properties from measurements.
Interdigital sensors consist of alternating parts of long, thin electrodes
on a plane. An ideal
model assumes that the periodic structure extends to infinity and the
electrodes have no
thickness. We extend the ideal analysis to account for the physical
thickness of the electrodes.
We also present the model in a matrix form which is amenable to linear
algebraic analysis
techniques. In particular, the "inverse problem" of estimating material
properties is formulated as
a generalized eigenvalue problem, which avoids the convergence problems
of previously used
iterative algorithms.
lon Beam Contouring to Generate Sub Millimeter Optics
Thomas G. Bifano, Mark N. Horenstein, Mike Feinberg, Prahsant Shanbhag
Boston University
110 Cummington Street, Boston, MA 02215
Phone: 617 353 5619, Fax: 617 353~659, Pager: 888 377~801
email: bifano@bu.edu
An ion beam microcontouring process has been developed for figuring
sub millimeter
diameter optics, characterized by aperture diameters less than 1 um
and precision of tens of
nanometers or better. A novel technique was developed to create such
optical contours on
suitable optical materials by etching with a narrow ion beam that is
rastered across a substrate.
Control of the time history of the rastering can be employed to generate
complex aspherical
shapes. The physical setup and procedure are described, as is the mathematical
contouring
algorithm and a number of simulations and empirical results.
The algorithm involves a deconvolution process in which the desired
removal contour and
ion beam profiles are synthesized as wavelet expansions. The ion beam
trajectory is then
computed using a wavelet deconvolution. The ion machining process is
to be carried out by
focussed beam sputtering. This involves a 100 um diameter focused ion
beam created by a
duoplasmatron ion source. The beam is directed to the target using
two orthogonal pairs of
electrostatic plates controlled by a computer guidance system. The
ion machining apparatus
comprises an ion source, a positionable sample stage and gauging devices
to monitor the
conditions of the chamber and the beam.
Complex three dimensional shapes were machined in single crystal silicon
and in nickel.
Results characterizing ion beam behavior, system performance and contouring
results are
presented.
A Micro Scale Electric lnduction Machine for a Micro Gas
Turbine
Generator
Steven F. Nagle and Jefferey H. Lang
Room 10 007, EECS Department
Massachusetts Institute of Technology
Cambridge, MA 02139
This paper describes a micro scale electric induction machine that is
designed to serve as
the starter and generator in a micro gas turbine generator. Its development
is part of the MIT
Micro Gas Turbine Generator project, which has the ambitious goal of
using MEMS fabrication
technologies to construct compact electric power systems from a gas
turbine generator
comprising a compressor, combustor, turbine and electric generator.
This system could exhibit a
power density 20 30 times more powerful than the most powerful Lithium
batteries today,
based on the energy density of hydrocarbon fuel sources [Epstein et
al., 1997]. It is possible
that the technology could be used to create compact, portable power
supplies.
This research has been aided by several previous research efforts concerning
micro motors.
Various types of micro motors have been given a great deal of attention
in the past ten years
[Tai, 1989; Lober and Howe, 1988; Bart, 1988; Mehregany, 1990]; and
several types of
variable capacitance micro motors have been fabricated and tested extensively
at MIT
[Mehregany et al., 1990; Bart et al., 1992; Tavrow et al, 1992]. We
have considered all
possible electric motor arrangements and chosen an electric induction
machine, as shown in
Figure I . At the outset, magnetic machines were ruled out due to issues
of incompatibility with
their fabrication processes. Also, permanent electret machines were
ruled out for lack of a suitable material. And any machine which would
require contact to the
rotor was ruled because of fabrication and friction concerns. Only
electric induction and
variable capacitance remained; and variable capacitance was ruled out
because of poor
performance and a more difficult fabrication sequence. Like their variable
capacitance counter
parts, electric induction micro motors have been studied in the past
[Bart and Lang, 1989];
however the research was meant only as a detailed introduction to the
subject. Our efforts to
date have treated the analysis and design of electric induction machines
from the ground up. The
goal of this research has been to develop an electric induction machine
exhibiting the highest
possible power density, with the highest efficiency possible, within
the severe design constraints
of its CMOSMEMS fabrication process and within the confines of its
host turbomachinery.
Production of Ions and Nanoparticles from Taylor Cone
Jets of
Highly Conducting Organic Electrolytes
J. Fernandez de la Mora and M. Gamero Castano
Mechanical Engineering Department
Yale University
New Haven, CT06520 8286, USA
delamora @torus.eng.yale.edu
Following the early studies by Zeleny [1] and Taylor [2] on electrified
liquid cones, their
richness of regimes was greatly clarified by Cloupeau and Prunet Foch,
who introduced the
more precise term 'conejet' [3, 4]. Research on the subject received
a formidable stimulus after
Fenn's discovery of multiply charged species in electrospray ionization
mass spectrometry [5].
In the following decade, a number of articles have investigated the
scaling laws determining the
diameter [6 10] and charge [11] carried by the drops formed after breakup
of these conejets.
Although a number of subtle disagreements remain, there is an approximate
consensus on the
nature of these laws in the limit of liquids with electrical conductivities
K above 10S/m, which
tend to produce micron or submicron jets. This is the most interesting
range for many
application, since no alternative process able to atomize a liquid
into such small drops is known.
In this limit, the jet current l is essentially independent of liquid
viscosity and meniscus voltage
(within the finite voltage range where the conejet is stable), depending
only on the flow rate Q of
liquid pushed through the jet as well as three physical properties
of the liquid: its surface tension
coefficient y, electrical conductivity K, and dielectric constant.
Control of Foodborne Pathogenic
Microorganisms Using Electric
Discharge Generated Ozone
Enhanced by Ultraviolet Photon
S. Edward Law and Michael E. Diaz
Department of Biological and Agricultural Engineering
Driftmier Engineering Center
University of Georgia
Athens, GA 30602 4435, USA
Email: edlaw@bae.uga.edu
A fundamental need of all societies worldwide is an adequate and safe
source of food.
Consumer conf~dence in food safety has become of paramount importance,
while at the same
time to remain competitive and environmentally sound, the US food processing
industry must
conserve input resources and more effectively treat process wastewaters.
Over the past ~8
years the use of chlorine based treatment of certain process waters
has raised concerns
regarding inadvertent formation of carcinogenic chlorinated hydrocarbon
compounds (e. g.,
trihalomethanes) in the water. Consequently, major water users such
as the pulp and paper
industry are relying less on chlorination and are phasing in alternative
treatments—principally
ozonation
Lumped Element Model for
Computing the Equilibrium
Charge Distribution Along a
Moving Web
Mark N. Horenstein
Dept. of Electrical and Computer Engineering
Boston University
8 Saint Mary's St.
Boston, MA 02215 USA
Ph: 617 353 9052 Fax: 617 353 6440 email: mnh@bu.edu
A lumped element model has been used to explain charge conduction and
convection in
stationary and moving web systems. Incremental sectors of the web are
assigned conductance
and their individual potentials are computed. Ordinary circuit equations
are used to determine
the evolution of the charge distribution. Results compare favorably
with the analytical solutions
of other authors.
Electrostatics plays an important role in the processing of textiles,
polymers, plastics, and
other insulators. Large sheets of these materials are commonly called
"webs." When a thin web
of insulating material is drawn over metal rollers or similar guiding
structures, contact
electrification can cause excess charge to build up, leading to arcing,
electrostatic discharge
(ESD), unwanted electrostatic forces, or undesirable dust precipitation.
The electrostatics of a
moving web system is a dynamic problem affected by surface conductivity,
surface layer
capacitance, geometry, and material motion. An analysis method that
predicts the charge distribution and
surface potential on a moving web can be a valuable tool when designing
web based
manufacturing systems, but direct mathematical analysis becomes difficult
in the complex
geometries found in many practical industrial situations. This paper
describes an analysis method
based on a discretized, lumped element representation of moving webs.
Charge conduction is
modeled using fixed value resistors, and charge convection is modeled
by direct material
transport over time. The analysis method can be applied to a wide variety
of geometries and
industrial situations and provides physical insight into the fundamental
electrostatic processes at
work in moving web systems. It also should be useful in predicting
the behavior of web systems
in which surface conductivity is non ohmic (i. e., nonlinear.)
Relating Roller Shaft \/oltages to
Tribocharging During Sheet
Transport
Humphrey Wong
Surface Modification ar1d Electrostatics Unit, MR&E, IMMPC
Eastman Kodak Company
Rochester, NY 14652
Printers often employ pinch rollers in order to convey sheets of material
from storage
cassettes, through a printing operation, and sometimes through a development
station before
finally depositing the sheets into a receiving area. Transport of sheets
through pairs of pinch
rollers can result in tribocharging both the rollers and the sheets.
By monitoring the end shafts of
certain types of pinch rollers with voltmeters, it is possible to relate
the voltage vs. time behavior
to the tribocharging taking place during passage of the sheets through
the pinch rollers. In this
paper, we will present an interpretation of various voltage signals
in terms of the charging and
discharging characteristics of the roller and sheet surfaces.
The Effects of Electric Field Radiated from Electrostatic
Discharge on the Electronic Circuit
Jiu sheng Huang
9th Department
Beijing Research Institute of Special Electromechanical Technologies
No. 1, Bei yuan Da Yan, An Ding Men Wai
Beijing, China, 100012
Tel: 86 1~66749396~5
E mail: jiushuang@263.net
This transient electric field radiated from charged human body discharging
to the ground and
from the ESD simulator are studied. Many waveforms and spectrums of
the field from the ESD
are analyzed. The effects of the field to typical electronic circuits
are studied.
A Theoretical Paradox Related to
Solid Dielectrics that Cannot be
Resolved Even After a Computer
Simulation Using Finite Element Analysis
Andreas Trupp
atrupp@hotmail.com
It is demonstrated that two common methods of determining the mechanical
force acting
between two electrified bodies, that is Coulomb's law on the one hand,
and the method of
virtual work on the other hand, yield results that differ from each
other if dielectrics are involved.
Piezoelectric Effects in Ice
Hasashi Shio
Department of Physics, Hokkaido University, Japan
Fax: 81 11884 6184
Charging mechanisms of ice are generally based on the temperature gradient
theory in which
the electric potential is formulated as V = 2~1T (mV), where V is a
electric potential difference
between two specimens, and T is the temperature difference between
them. If the temperature
difference is 30 •C, the electric potential difference becomes only
60 mV. On the other hand,
when two ice specimens are asymmetrically rubbed together the electric
potential difference
reaches to above I V. As a result, it is suggested that the charging
mechanism is based on a
different origin from the temperature gradient. In order to research
this new origin of the
charging mechanism of ice, the dependence of the charging phenomena
of ice on stress of the
specimens is investigated.
A New Unified Method for
Measurement of Electrical
Resistivity of Textile Assemblies
Pellumb G. Berberi
Department of Physics
Polytechnic University of Tirana
Tirana, Albania
A new multiple step method for measuring electrical resistivity of textile
assemblies is
proposed that takes compressional properties of the assembly into consideration.
A new
parameter is introduced to describe electrical resistivity of textile
materials as the limit resistivity
of a compressed fiber assembly. This new definition approaches the
measured resistance of the
textile assembly as something similar to the volume resistivity of
a rigid homogeneous material.
Experiments carried out with different kinds of fiber assemblies clearly
show that the electrical
resistivity so defined is an inherent characteristic reflecting the.
and is independent of sample form
(fabric, yarn, fiber).electrical properties of fiber material.
A Method to Estimate the Area of Contact of a Textile
Fabric
with a Rigid Flat Surface
Pellumb G. Berberi, J. Amirbayatt, I. Poratt
Department of Physics
The Polytechnic University of Tirana
Tirana, Albania
TDepartment of Textiles, UMIST
Manchester, UK
The true area of contact of two surfaces is an important parameter to
be estimated when electrostatic propensity,
surface resistivity, frictional resistance, or any other property of
the surfaces are to be measured [1, 2, 7]. Some
methods for testing of electrostatic properties of textiles as 'decay
time,' 'frictional charge' or 'electrical surface
resistance' are known, among others, for their low reproducibility
due to the uncontrolled alteration of 'true area of
contact' [3, 6].
Several attempts have been reported by different authors for the estimation
of the area of apparent contact
between metal and a flat polymer sheet by measuring the imprint made
on the polymer surface by a travelling
microscope [4, 5]. Naturally, this method can not be used to estimate
the area of contact of a textile fabric with a flat
rigid surface because of relatively high surface asperities.
To the best of authors' knowledge, there is no work published which
describes the objective measurement of
contact area of a textile material with a flat rigid surface.
