Abstracts
from the ESA 2000 Annual Conference Proceedings
June 19-21, 2000
Brock University, St. Catherines, Ontario
Keynote:
Where in the USA is Electrostatics?
Joseph
M. Crowley
Electrostatic
Applications
Morgan
Hill, CA 95037
Electrostatics
is a field with many applications, and it is often difficult
for
one person to gain an understanding of all the various lines of inquiry
that
are taking place. In order to discover where electrostatics work is
carried
out in the United States, a number of lists of people active in
electrostatics
were analyzed and compared. These lists involve participants
in
meetings, members of organizations, authors, and customers of an
electrostatics
bookstore.
This
analysis shows that active participation in electrostatics is much
more
widely dispersed than might be obvious from any individual's direct
experience.
Although there are a few large clusters of organizations like
Xerox
and Hewlett-Packard, most of the workers are in much smaller
organizations
spread out over all the states, with little apparent
interaction.
In
addition, most people appear only on a single list, suggesting that
these
lists are merely small samples from a much larger population. Using
techniques
adapted from population biology, the overlap of the lists is
used to
estimate the total number of people in the USA working in
electrostatics.
The number is probably in the tens of thousands. Some of
the
implications of these results for the future of the ESA are discussed.
Importance of Electrostatics in
Respiratory Drug Delivery
Joanne
Peart, Ph. D.
Virginia
Commonwealth University
Richmond,
VA
Respiratory
drug delivery has historically disregarded the subject of
electrostatics.
Models of aerosol deposition in the human lung are based on
data
collected following inhalation of `charge neutralized' aerosol
particles
(Task Group on Lung Dynamics, 1966), despite studies which have
shown
dramatic deposition changes as a function of aerosol charge
(Melandri,
1983; Balachandran, 1991; Bailey 1997). Recently, the paradigm
has
changed, as aerosol electrostatics represents an important and emerging
property
of pharmaceutical aerosols. Therapeutic aerosols generated by
nebulizers,
pressurized metered dose inhalers (pMDIs), and dry powder
inhalers
(DPIs) are known to be charged. Moreover, the practical
significance
of electrostatic charge interactions to the functionality of
therapeutic
aerosols embraces most aspects of their processing and general
use,
including their formulation and manufacture, dosing reproducibility
and
deposition behavior within the respiratory tract and/or spacer devices.
Electrostatic
properties of the potentially respirable aerosol clouds
generated
by high efficiency DPIs (Turbohaler© and Dryhaler©) have been
shown
to be dependent upon the physical and chemical properties of the
powder
under investigation, as well as the construction and deaggregation
mechanism
of the inhaler (Byron, 1997). Figure 1 illustrates the net fine
particle
dose charge of aerosols generated by commercially available pMDIs.
Both albuterol
chlorofluorocarbon (CFC) and hydrofluoroalkane (HFA) MDIs
conferred
net electronegative charges on their fine particle clouds of the
order
of -160 pC, despite their different propellant systems, drug salt
forms,
drug concentrations and metering volumes. A systematic investigation
of
the formulation components' contribution to the measured charge showed
significant
differences between the CFC and HFA based albuterol systems
(Peart,
1998). Electrostatic charges of respirable particles determined in
these
studies have enabled us to speculate whether such charged particles
would
be expected to influence regional drug deposition in the respiratory
tract.
AccudepÆ-A Revolutionary Process
Technology for Manufacturing of
Pharmaceuticals
M.
Kashef, S. Chrai, A. Katdare, R. Murari, G. Santonastaso
Delsys
Pharmaceutical Corp.
Princeton,
NJ
AccudepÆ
technology is a manufacturing process based on electrostatic
deposition.
This technology provides a simple manufacturing process for
deposition
of active pharmaceutical drugs on a multitude of substrates.
Majority
of active pharmaceutical drugs is in the form of dry powders with
different
morphologies varying in size from sub-micron to greater than 100
microns.
Using these powders as primary raw material, traditional
pharmaceutical
manufacturing applies a sequence of manufacturing operations
that
consists of mixing and blending powders, granulation, drying,
lubrication,
compression and coating. Each step requires employment of
strict
quality control procedures that add cost and cycle time without
adding
any value. The final product, also known as finished dosage form,
consists
of a small amount of therapeutically active drug substance, mixed
with
a large quantity of inactive excipients. AccudepÆ technology replaces
all
these steps with single electrostatic deposition process equipment and
eliminates
most of the inactive excipients.
In
AccudepÆ technology pharmaceutical powders are transported from the
hopper
to the next unit wherein electrostatic charging of the powder takes
place.
Subsequently, the powder is moved to the next module, which
disperses
the powder into a homogeneous and uniform cloud of particles.
These
charged particles accelerate to the opposite end of the chamber and
deposit
on predetermined areas of a receiver covered with a
pharmaceutically
acceptable polymer film. The receiver is a planar surface
consisting
of a ground plane surrounding a matrix of deposition electrodes.
These
individual electrodes are ultimate resting-places of the
pharmaceutical
powders that have entered the chamber. These deposition
electrodes
are electrically insulated from the ground plane by dielectric
media.
By applying the proper potential between the electrodes and the
ground
plane one can direct charged pharmaceutical particles to the
deposition
sites.
Actual
mass and bioavailability of the active drug in any dispensed
medicine
determines its efficacy. The efficacy can vary from minimal to
therapeutic
target or even toxicity depending on the dose of the
administered
drug and the patient. Measuring active drug content of
finished
dosage form is a destructive, and expensive, test process. Hence,
current
regulation allows manufacturers to use random sampling and
well-defined
statistical methods to pass or fail batches. Due to the nature
of
this test process, batches of drugs are released to the market that are
recalled
later. This process costs tens of millions of dollars, not to
mention
adverse effects on patients.
AccudepÆ
technology enables manufacturing of drugs with much higher
accuracy
and provides an economical way for nondestructive testing of the
product
that can be used to measure the active drug content of every
individual
dose.
Pharmaceutical
powders have a wide range of physical, electrical, chemical
and
mechanical properties. Active research is conducted to develop metrics
for
measuring those powder characteristics that play a role in AccudepÆ
process.
Knowing these parameters will enable us to fine-tune the process
to
each drug and create a recipe that can be used to optimize manufacturing
process.
Furthermore, it will provide the road map for future enhancements
to
the design and manufacturing of the machinery used in AccudepÆ process.
Several
pharmaceutical powders have been characterized and successfully
deposited
using AccudepÆ technology. The dose amount for these depositions
varies
from micrograms to several milligrams. These depositions have been
processed
into final dosage forms with different formats, including those
used
in current pharmaceutical manufacturing.
Compatibility
studies have shown that AccudepÆ technology can improve drug
stability
thereby creating new or expanded commercial applications for new
or
current drug products.
Animal
studies have produced successful results for the technology and
human
studies will be conducted before the end of the current year.
The
research and development in this technology is conducted by Delsys
Pharmaceutical
Corp. in close collaboration and partnership with major
pharmaceutical
companies in the US and Europe.
Microscale Electrostatics in Mitosis and
Cytokinesis
L.
John Gagliardi
Department
of Physics
Rutgers
University
gagliard@crab.rutgers.edu
Tel:
856 225 6159
Primitive
biological cells had to divide with very little biology. This
paper
proposes physicochemical mechanisms based upon microscale
electrostatics
which explain and unify the basic motions during mitosis
(nuclear
division) and cytokinesis (cytoplasmic division): (1) assembly of
the
asters, (2) motion of the asters to the poles, (3) poleward motion of
chromosomes
(anaphase A), and (4) cell elongation (anaphase B). In the
cytoplasmic
medium which exists in biological cells, electrostatic fields
are
subject to strong attenuation by ionic screening, and therefore
decrease
rapidly over a distance of several Debye lengths. However, the
presence
of microtubules within cells changes the situation completely.
Microtubule
dimer subunits are electric dipolar structures, and can act as
intermediaries
which extend the reach of the electrostatic interaction over
cellular
distances.
Experimental
studies have shown that intracellular pH rises to a peak at
mitosis,
and decreases steadily through cytokinesis and furrowing. This
result,
in conjunction with the electric dipole nature of microtubule
subunits,
is sufficient to explain the dynamics of the above motions,
including
their timing and sequencing. In addition, the model can also be
extended
to incorporate the complex motions during prometaphase
(congression)
and alignment at the metaphase plate. In order to keep the
discussion
within manageable bounds, prometaphase motion will not be
addressed
in this paper. The physicochemical mechanisms utilized by
primitive
cells could provide clues regarding our understanding of the
important
problem of cell division in modern eukaryotic cells.
Novel Applications of Electrostatic
Spraying Technology
Steven
C. Cooper1 and S. Edward Law2
1Electrostatic
Spraying Systems, Inc.
Watkinsville,
GA
2The
University of Georgia
Biological
and Agricultural Engineering
Athens,
Georgia
An
improved air-assisted induction-charging electrostatic spray nozzle has
been
jointly developed by The University of Georgia and Electrostatic
Spraying
Systems, Inc. This spray charging nozzle is for liquids with
resistivity
in the range of between 25 ohm-cm to 10 megohm-cm. Charging
levels
achieved are 5 to 10 mC/kg for liquid flow rates in the range of 80
to
200 ml/minute. Primarily the charging nozzle was intended for
water-based
agricultural pesticide and foliar fertilizer applications onto
plant
targets. Various large agricultural spray machines have been
developed
and are now being sold commercially. The largest of these
tractor-mounted
field sprayers have over 100 electrostatic nozzles. Over
one
million acres of cropland are now routinely treated with electrostatic
field
sprayers using this new technology. Growers typically use half the
amount
of pesticide compared to conventional spraying methods. Other
agricultural
applications include sprayers for postharvest bananas and
vineyard
spray systems for wine and table grapes.
In
addition to agricultural applications, several unique industrial
applications
have recently been developed commercially. Perhaps the most
unique
is the new cosmetic skin tanning system. This electrostatic sprayer
dispenses
a lotion evenly over the skin, resulting in a cosmetic tan in
about
one minute while eliminating the concern of hazardous ultraviolet
radiation
associated with other skin tanning methods.
Electrostatic Coating of Popcorn
Sheryl
A. Barringer and Peggy Miller
Department
of Food Science and Technology
The
Ohio State University
2121
Fyffe Road
Columbus,
OH 43210
Introduction
Electrostatic
coating technology was introduced to the metal painting
industry
in the 1960s. The solvent-based liquid paints were converted to
dry
powders containing pigments, binders, fillers, and hardeners. By
applying
the powdered paint using electrostatic spray guns, and melting
that
powder onto the metal, a more even coating is produced. Research on
electrostatic
technology has been taken from powder coating in the painting
industry
and adjusted to suit the food sector (Anon., 1996).
Snack
foods such as potato chips, pretzels, popcorn and tortilla chips are
coated
with salt, cheese powder and assorted seasonings. The amount of
seasoning
is very important to the consumer, so the producer has to make
certain
the snacks are completely and evenly coated on all sides. Powders
used
for coating snack foods are applied by means of sprinkling systems
such
as rollers, screw distributors and anti-static atomization systems
(Anon.,
1993). The equipment can be very complex or as simple as seasonings
dropping
from a pipe into a tumbling drum. These methods prove to be very
haphazard
and often result in a poor distribution of flavor onto the
product,
severe flavor overuse and contamination of conveyors and weighing
equipment
(Anon., 1996; Pannell, 1980). With traditional seasoning methods,
it is
not uncommon for a snack manufacturer to put 30% and, in some cases,
as
much as 50% more seasoning than actually needed into a drum because of
the
expected waste incurred with these types of seasoning processes (Anon.,
1992).
This waste becomes an economic concern due to the high price of
seasonings
used on snack foods.
The
basis of electrostatic coating is the attraction between the negatively
charged
seasoning, in this case the salt, and the nearest earthed object,
the
food product (Anon., 1980). The seasoning is dispersed from a tube and
introduced
to a charge created by a wire. When the seasoning passes through
the
corona zone created by the charge on the wire, the seasoning picks up
the
charge and seeks out the nearest ground state, the product to be coated
or
the drum.
The
charged particles are allowed to fall onto the product, where they tend
to
separate and distribute themselves evenly. This separation and
distribution
is caused by the charges on the seasoning repelling each
other.
Electrostatic attraction helps to achieve a more homogenous coating
even
on difficult shapes and gives a considerable reduction in flavor
falloff
(Anon., 1996).
Using
electrostatic coating methods eliminates the problems associated with
traditional
coating methods. However, the size and the shape of the coating
material
may have a large effect on the transfer efficiency when using
electrostatic
coating methods (Mazumder et al. 1997). A more efficient
electrostatic
coating system provides more seasoning to the food product
with
less wasted seasoning. The purpose of this study was to determine the
effect
of seasoning size and shape on efficiency of electrostatic coating.
Temperature Dependence of DC Corona and
Ion Entrainment in a Flow Channel
Charles
G. Noll
ITW
Static Control and Air Products
2257
North Penn Road
Hatfield,
PA 19440-1998
Tel:
215-822-2171, Fax: 215-822-3795
email:
ir000382@mindspring.com
Abstract
Current-voltage
(I-V) data for positive and negative polarity
point-to-plane
geometries are reported for gas flows transverse to the axis
of
the emitters. Air and nitrogen flows from zero to 5 m/s were considered
in
the experiments and temperatures from 213 K to 493 K in nitrogen and 283
K to
493 K in air. Carrier entrainment from the individual corona and
positive-negative
polarity emitter-pairs were considered towards
understanding
the static elimination process.
Charge Extraction from the Carrier Stream
that is Entrained from DC Corona
by Flowing Air and Nitrogen Gases
Charles
G. Noll
ITW
Static Control and Air Products
SIMCO
Static Control and Cleanroom Products
2257
North Penn Road
Hatfield,
PA 19440-1998
Abstract
Charge
decay has been studied in a cylindrical flow channel with a pair of
point-to-plane
emitters. It was found that charge decay is determined by
the
type of corona and gas speed, and not so much by the magnitudes of the
corona
currents.
Carrier Entrainment from a Radioactive
Ionizer in Flowing Air and Nitrogen
Charles G. Noll1, William Miller2 and
Christopher Bracikowski2
1ITW
Static Control and Air Products
2257
North Penn Road
Hatfield,
PA 19440-1998
2Department
of Physics
Bloomsburg
University
Harltine
Science Center
Bloomsburg,
PA 17015
Abstract
Unlike
electrical corona, radioactive ionizers produce positive and negative carrier
pairs in the absence of an external electric field. In this work we
study
the entrainment and extraction of carriers from an air or nitrogen
stream
that is blown over ionizer. The results
are compared with those
from
corona ionizers where electric fields are used to generate and strip
carrier
species from the gas stream.
Modeling of Surface Charge Dissipation on
Fabrics
J. A.
Gonzalez
Department
of Clothing and Textiles
University
of Manitoba
Winnipeg,
MB, Canada, R3T 2N2
Tel:
(204) 474-8065, Fax: (204) 474-7592
E-mail:
gonzale0@ms.umanitoba.ca
Abstract
This
paper describes the development of a theoretical model for
characterizing
textile fibers in terms of charge dissipation. Charging and
decay
of charge are considered a function of time and time constant of the
material.
Twenty-four fabrics with different fiber content and blends were
evaluated
and characterized at 30% relative humidity and room temperature.
A
charging-dissipation model was developed identifying five parameters on a
waveform.
Various theoretical considerations have been drawn in explaining
why
textile fibers yield distinct dissipation waveforms. Relationship among
polymer
structure, fiber moisture content, environmental conditions, and
the
identified five parameters of the proposed charging-dissipation model
has
been determined.
Charge on Corona-Treated High Density
Polyethylene Bottles
J. M.
Singley, V. J. Urick, C. Bracikowski, and C. G. Noll
1Department
of Physics
Bloomsburg
University
Hartline
Science Center
Bloomsburg,
Pennsylvania 17815-1301
2ITW
Static Control and Air Products
2257
North Penn Road
Hatfield,
PA 19440-1998
Abstract
The
elimination of static charge from corona-treated articles has been a
challenge
for many years, yet few systematic investigations have been
reported.
In this preliminary report we summarize literature and present
early
experiments and modeling efforts towards understanding the
distribution
of charge on cylindrical bottles before and after corona
treating.
The results are discussed in terms of Gauss's Law and several
static
elimination approaches.
Marking with Electrostatics
Dan
A. Hays
Xerox
Corporation
Wilson
Center for Research & Technology
Webster,
NY 14580 USA
Copying
and printing technologies based on electrostatic marking have
evolved
to high levels of performance over the past 40 years. Xerography is
the
dominant electrostatic marking technology with an estimated 50 billion
dollars
a year in worldwide revenues. The invention of xerography by
Chester
Carlson on October 22, 1938 was the genesis of a major innovation
during
this century. Carlson's invention was influenced by the earlier work
of
Paul Selenyi, a Hungarian physicist, who was the first to record images
with
an electrostatic marking process in which a modulated ion source was
scanned
over an insulating layer to form an electrostatic image that was
subsequently
developed with powder. Carlson's insight was to use a
photoconductive
material to produce an electrostatic image that is then
developed
with charged, pigmented powder. Carlson built a prototype of a
copying
machine, but was unsuccessful in attracting the interest of large
corporations.
In 1944, Battelle Memorial Institute in Columbus, Ohio began
work
on the process where key advances were made in materials and
processes.
This led to the introduction of the highly successful Xerox 914
plain
paper copier in 1959.
Electrostatic
marking technologies utilize an electrostatic force acting on
pigmented
particles to form an image that is deposited on a medium such as
paper.
The electrostatic force can be approximated as
where is the charge
on the
particle and E is the applied electric field. To form an image with
charged
particles, a variation (spatial or temporal) in the electrostatic
force
is required. For insulating particles, the variation in can be
expressed
as . The first term describes a class of imaging physics in which
a
variation in E acting on charged particles causes an image-wise variation
in
the electrostatic force. The xerographic process is a good example of
the imaging class in which the spatial variation
in dE is produced by
image-wise
light exposure of a charged photoreceptor. The imaging class has
not
been commercialized. If the pigmented particles are conducting and in
contact
with an electrode or other conductive particles in the presence of
an
electric field, a charge will be induced on the particles that is
proportional
to the applied electric field. This represents a third class
of
imaging physics in which is
proportional to the square of . Several
types
of electrostatic marking systems based on the above classes of
imaging
can be identified for either indirect or direct printing onto paper
[Hays,
1999].
The
current high levels of performance for electrostatic marking systems
can
be attributed to a multitude of material and process advances. The
quality
of images depends on the control of toner particle charge and
adhesion.
Triboelectricity is the dominant method for charging particles,
in
spite of a poor understanding of microscopic mechanisms and the
enhancement
of adhesion due to a nonuniform surface charge.
Vibrational Fluxmeters-A New Class of
Electric Field Sensors
V. I.
Struminsky
Sobolev
Institute of Mathematics
Novosibirsk,
Russia
Abstract
For
measurement the strength of a slowly varying (quasi-static) electric
field,
usually electrostatic fluxmeters (field mills) with dynamic
transformation
of field strength into AC-signal are used. Two main versions
of
the marked devices with cylindrical and flat measuring electrodes are
known.
The operation of these devices is based on periodic modulation of
the
electrode area exposed to the field under measuring by means of
electrode
rotation or periodical shielding by a rotating screen.
New
kinds of dynamic transformers-electric field sensors recently are
developed,
at which the vibration of electrode is used instead of the
rotation.
In some fields of application these sensors have advantages in
comparison
with traditional fluxmeters. Absence of rotating parts and
leak-proofness
of transformers leads to appreciably longer original life,
that
is important for long-time monitoring, for example, in atmospheric and
geophysical
experiments. High frequency of transformation, small area of
the
electrodes and practically complete absence of electrode area
modulation-all
these allow using vibrational sensors for measurements in
medium
with a high electrical conductivity and convective current.
In
this paper theoretical basics of transformation process on an example of
the
sensor are presented, at which the modulation of an electric field
occurs
by vibrating string resonator. The example of concrete model of the
sensor
is given which was originally designed for thunderstorm electricity
observation
and then was used also for continental and oceanic
investigations
of good weather atmospheric electricity. The brief
description
of a miniature electric field sensor is given which was
designed
by a group of researchers of Novosibirsk State University for
control
of spacecraft surface charging and space electricity research and
successfully
used in space investigations.
Operating
conditions of measuring equipment in industrial applications are
usually
not so strong than in a free atmosphere or in space. The
vibrational
sensors can widely be used for the control of electrostatic
effects
and hazards in various industrial instrumentations.
An Electrostatic Field Transducer with
High Immunity to Parasitic Voltages
Liviu
Matei, Mihai Antoniu, Cristian Ze, Gh. Antoniu
Technical
University "Gh. Asachi"
Bd.
D. Mangeron 53
Iasi
6600, Romania
lmatei@ee.tuiasi.ro
Abstract
The
paper presents a fieldmill electrostatic transducer with two output
signals
from field sensor. The output signals are sinusoidal voltages with
the
same frequency but have opposite phase. A differential amplifier DA
sums
these voltages and subtracts parasitic voltages. The output voltages
of DA
have the same frequency but double amplitude and very small parasitic
components.
Proposed solution was tested on portable model (gun-like).
An Improved Experimental Setup for
Electrostatic Discharge Measurements
Based on the Transmission Line Pulsing
Technique
J. C.
Lee1, W. R. Young2, J. J. Liou1,
G. D.
Croft2, and J. C. Bernier3
1Electrical
and Computer Engineering Department
University
of Central Florida
Orlando,
FL 32816
2Technology
Development Department
Intersil
Corp.
Melbourne,
FL 32902
3Reliability
Engineering Department
Intersil
Corp.
Melbourne,
FL 32902
Abstract
Transmission
line pulsing (TLP) is a useful technique to characterize
electrostatic
discharge (ESD) events in semiconductor devices. The pulse
waveforms
generated by a traditional TLP setup, however, are often
distorted
by signal reflections. In this paper, a new and simple
experimental
setup is developed to improve the waveforms and deliver higher
current
to the device under test (DUT). The setup employs a modified
voltage
probe and a R/2R termination network.
New Approaches for Testing Materials
John
Chubb
John
Chubb Instrumentation
Unit
30, Lansdown Industrial Estate
Gloucester
Road, Cheltenham, GL51 8PL, UK.
Tel:
+44 (0) 1242 573347 Fax: +44 (0)
1242 251388
email:
jchubb@jci.co.uk
Abstract:
Materials
can be assessed for risks from static electricity by measurement
of
`charge decay' and by measurement of `capacitance loading.' This paper
describes
appropriate experimental methods for these measurements and
reports
the results of studies on a variety of materials in various test
conditions.
Methodological Aspects of Electric Field
Measurements in the Stratosphere
and Mesosphere
V. I.
Struminsky
Sobolev
Institute of Mathematics
Novosibirsk,
Russia
Abstract
From
methodological point of view electric field measurements in the
strato-mesosphere
are match more difficult than at the ground level. It is
in
general because of the influence of various environment factors on the
measurement
process. The main factors are the motion of an electric field
sensor
relative to the medium, complex composition of charged particles,
varying
air conductivity, presence of streams of energetic particles and
UV-radiation
and so on. In this paper some methodological aspects of
electric
field measurements in conductive medium in the presence of
displacement,
conductive and convective currents are discussed. Basic
principles
of theory of "double probe" method are considered in the
presence
of probe rotation. Some recommendations for reducing the influence
of
the last two components of complete current on the accuracy of
measurement
results are proposed.
A System for the Advance Warning of Risk
of Lightning
John
Chubb and John Harbour
John
Chubb Instrumentation
Unit 30,
Lansdown Industrial Estate
Gloucester
Road
Cheltenham,
GL51 8PL, UK.
Tel:
+44 (0) 1242 573347 Fax: +44
(0) 1242 251388
email:
jchubb@jci.co.uk
Abstract
The
design and performance of a system is described to provide advance
warning
of the risk of local lightning on the basis of observations of
atmospheric
electric field, radio noise and lightning impulse signal
activity.
The values of these parameters are assessed to provide two levels
of
warning.
Effect of Surface Coverage of a Glass Pipe
by Small Particles on the
Triboelectrification
of Glucose Powder
Matti
Murtomaa1 and Ensio Laine
Laboratory
of Industrial Physics, Department of Physics
University
of Turku, FIN-20014 Turku, Finland
Tel.;
+358-2-333-5735; fax: +358-2-333-5993.
E-mail
address: matti.murtomaa@utu.fi
1Corresponding
author.
Also
Graduate School of Materials Research, Turku, Finland.
Abstract
This
paper presents the results of an experimental study on the
triboelectrification
of glucose powder in a glass pipe, and the role of
smaller
particles of different material mixed with the main phase. Mixtures
of
different concentrations were charged by sliding them down into the
Faraday's
cup via a glass pipe. The influence of sticking to the inner
surface
of the pipe was examined with a microscope equipped with camera and
an
image analysis program. Smaller particles at the pipe surface partly
change
the glucose-glass-contacts to the glucose-adhered powder-contacts
and this
has a significant effect on the sign and the amount of transferred
charge.
The relative coverage of the glass pipe by small particles can be
used
as a measure of the charging ability of an additive, and can also give
information
of the sufficient amount of additive which would lead to
neutral
charge.
Evolutionary Changes of Thin-dielectric
Charging by Positive Point DC Corona
T. S.
Lee
Department
of Electrical and Computer Engineering
University
of Minnesota
Minneapolis,
MN
Abstract
Potential
scanning was earlier used to measure long-term charge retention
behavior
on a dielectric sheet following the onset of positive point
corona.
A thin oil film provided visualization, showing circular domain
structure
in expansion. Being repeatable, this phenomenon has been further
studied
by scanning sequences consecutively and separately obtained in
intervals
of a few seconds. The results are consistent with projections of
a
self-limiting evolutionary charging theory previously considered.
A Relationship between Mesh, Grit and
Particle Diameter
Albert
E. Seaver
3M
Engineering Systems Technology Center
3M
Center Bldg. 518-1-01
St.
Paul, MN 55144-1000
Tel:
(651) 733-8629 Fax: (651)
736-3122
e-mail:
aeseaver@mmm.com
Abstract
Electrostatics
is often used to control the motion and placement of small
particles.
In many applications a broad distribution of particles is first
"cut"
into a narrow particle size range by sieving or screening. This group
of
sieved particles becomes the particle distribution used in the
application.
In these situations the average particle diameter in the cut,
which
is not much different from the largest or smallest diameter particle,
becomes
the effective particle diameter used in the electrostatic
calculations.
However, when particles are sieved or screened their size is
most
often listed by the size of the mesh or screen used to classify the
particles.
This leaves the person about to make a calculation scurrying
around
trying to find the conversion between the screen size and the actual
particle
size. For example, the average particle size of a "cut" is most
often
referred to as the grit (or grit size or grit number) or
interchangeably
as the mesh (or mesh number) or simply as the grit mesh. In
this
paper a comparison table is presented listing the average particle
size
and mesh number values for various standards (ANSI, FEPA, ISO, JIS and
the
Tyler Standard Screen Scale) in use today. Based on the definition of
the
mesh number a simple model of the sieving or screening process is
presented.
The model is used to give a mathematical relationship between
average
particle diameter and grit size or mesh number for a cut. The
simple
relationship [or ] is shown to predict
(30%) the connection between
the
average particle size and the grit or
mesh number M for all the screen
standards
when the particle size is large (> 80 m), and this relationship
is
also found to be reasonably accurate for micropowders described by the
FEPA-P
standard.
Simulation of the Separation of Free Falling
Bipolar Charged Particles
through a Vertical Cascade Array of
Faraday Pails
H.
Zhao, G. S. P. Castle, and I. I. Inculet
Applied
Electrostatics Research Centre
Department
of Electrical and Computer Engineering
University
of Western Ontario
London,
ON, Canada, N6A 5B9
Abstract
Experimentally
it was found that when a sample of bipolar charged powder
was
freely dropped from a height, the charged particles would separate in
vertical
and horizontal directions. The separation was based on the charge,
size
and mass of individual particles and other particles around them. A
computational
model was developed by Ali to model the dropping process of a
batch
sample of powder poured vertically from a height [1]. This model was
extended
here to simulate the separation processes of free falling charged
particles
passing through a vertical cascade array of Faraday pails. The
difference
with Ali's work [1] was that the boundary constraint imposed by
the
vertical Faraday pail array was introduced in the model since the
movement
of the bipolar charged powder was restricted by these boundaries during the
falling process. The model presented here takes into account electric
al,
drag and gravitational forces acting on each particle.
In
the experiments, the vertical array of Faraday pails consisted of seven
Faraday
pails, six special Faraday pails and one normal one, which were
mounted
vertically in cascade. The normal Faraday pail was located at the
bottom.
Each Faraday pail consisted of an inner cylinder and an outer
cylinder
pail. The inner and outer pails of the special Faraday pails had
open
holes on the upper and lower covers.
The
vertical array of Faraday pail sensors can be used to partially
separate
the bipolar charged polydisperse powder and measure the charge to
mass
ratio (Q/M) distribution of the powder deposited in each Faraday pail.
The
separation forces are due to the gravity segregation and space charge
repulsion.
Depending on the trajectories of particles in the free falling
processes
of the bipolar charged polydisperse powder, the particles were
selectively
collected in the vertical array of Faraday pails according to
their
charge, size, and mass thus providing a measure of the Q/M
distribution
of the charged particles. In the experiment, the particles
were
charged in an earthed metallic fluidized bed, selectively sampled at
different
depths of the bed through an axial sampling tube and dropped
through
the vertical array of Faraday pails. Three kinds of commercial
polymer
powders were used, referred to as A, B and C. Powder A, B and C are
all
polyamide powders. Powder A and B contain 3% of TiO2 as an
extraparticulate
additive and 0.48 ppm of chemically combined pigments.
Powder
A is the original powder from the packed powder bag and powder B is
obtained
from the industrial fluidized bed after working for a long period
time.
Powder C contains 8% of TiO2 chemically combined with the polymer.
This
model is compared to the experimental results and further documents
the
presence of bipolar charging of polymer powders in fluidized beds.
Experimental
results show that even though the net charge may be positive
(C)
or negative (A, B), the smaller particles are charged negatively and
possess
high Q/M value, while the larger particles are charged positively
and
possess lower Q/M.
Electric Field Distortion by Water
Droplets and their Deformation on
Insulator Surface
Ivan
J. S. Lopes, Shesha H. Jayaram, and Edward A. Cherney
University
of Waterloo
Electrical
& Computer Engineering Department
Waterloo,
ON, Canada
The
use of polymeric materials for outdoor insulation has increased
continuously
in the last few years mainly because of their improved
performance
under wet and contaminated conditions when compared to
conventional
porcelain and glass technology [1]. This is due to their
hydrophobic
surface property, which prevents water filming and development
of
leakage current. Because of their hydrophobicity, polymer outdoor
insulators
are partially wet more often than completely wet, and their
flashover
mechanism, in some cases named sudden flashover, is different and
yet
not well understood [2-4].
In
this work, the problem of the field distortion along a partially wet
insulating
surface is addressed. The behaviour of water droplets on a
commercial
polymer insulator exposed to AC voltage and their deformation on
the
surface is investigated experimentally [5]. The field distribution
along
the surface is numerically evaluated using Ansoft? 2D package (Figure
1).
The results show the field distortion along the insulator surface due
to
the partially wet condition. The experiments are carried out to evaluate
the
electric field enhancement on the surface due to the droplets.
Deformation
and elongation of the water droplets have been observed and are
reported
(Figure 2).
A
partial discharge measuring system has been used to detect corona from
the
tips of the droplets. The experiments, together with the field
calculations,
are helpful to understand the flashover mechanism of polymer
insulation.
The Treatment of Liquids Using Electric
and Magnetic Fields
G. F.
Girda
Applied
Electrostatics Research Centre
University
of Western Ontario
London,
Canada
Abstract
Several
different methods of liquid treatment using electric and magnetic
fields
are reviewed, focusing upon the use of high electric fields in
coalescence
of water droplets in water-in-oil emulsions and the use of
permanent
magnetic fields for scale removal in flowing water pipes.
Electrocoalescence
involves the use of high electric fields to produce the
growth
of water droplets in water-in-oil emulsions. The main factors that
influence
this process are discussed. In particular, results are described
for
an emulsion of water droplets in oil at concentrations of 0.9% and
4.5%.
This emulsion is subjected to an intense electric field applied via
insulated
electrodes. The dependence of volume mean diameter as a function
of
exposure time to the applied electric field and as a function of peak
applied
voltage in the electrocoalescer are presented.
Considerable
controversy exists regarding the use of permanent magnetic
fields
to remove scale in water pipes. One theory that could explain how
the
permanent magnetic field acts in order to stop and even remove the
scale
from the walls of pipes is presented, focusing on the main phenomena
that
take place in the water that contains calcium and magnesium
components.
An example of the scale removal by a magnetic field is shown
for
the treatment of a pipe after 3 and 6 months. The effect of the water
velocity
in the pipe upon the magnetic field treatment is also briefly
discussed
and how it is possible to reduce this dependency.
Despite
the established use of magnetic water treatment and the obviously
good
results obtained, a generally accepted theory still does not exist. It
remains
to continue research in order to find one and to solve the main
disadvantage
of magnetic water treatment, the permanent presence of
scale-causing
substances in water
Electrohydrodynamic Flow Associated with Unipolar
Charge Current due to
Corona Discharge from a Wire Enclosed in a
Rectangular Shield
James
Q. Feng
Xerox
Corporation
Wilson
Center for Research and Technology
800
Phillips Road
Webster,
NY 14580, USA
Unipolar
charge current can be generated through corona discharge from a
thin
wire enclosed in a shield electrode. Except for an ionization sheath
adjacent
to the coronating wire surface, most parts of the region in the
enclosing
shield contain drifting ions of a single polarity in response to
the
electric field. Momentum transfer as a consequence of collisions
between
drifting ions and electrically neutral air molecules gives rise to
the
electrohydrodynamic flow known as "corona wind." Although primarily
driven
by the Coulomb force due to unipolar charge in the electric field,
the
electrohydrodynamic flow cannot simply follow the direction of electric
field
lines because of the confinement of the solid walls of the shield.
Therefore,
the structure of the electrohydrodynamic flow can vary
significantly
depending on the system configuration. In the present work,
the
electrohydrodynamic flow in a rectangular shield is studied by solving
the
nonlinearly coupled governing equations via the Galerkin finite-element
method.
A highly symmetric system with the wire positioned at the center of
a
square shield is shown to contain eight equal-sized two-dimensional
recirculation
vortices. The number of recirculation vortices tends to be
reduced
by a slight asymmetry in the system. The flow structure of two
major
counter-rotating recirculation vortices is found to be most common in
systems
where the wire is positioned off the center of the rectangular
shield
in a two-dimensional domain. The results reported here may be
brought
to bear upon the "corona wind" effect in charging devices such as
corotrons
and scorotrons used in electrophotographic printing processes.
Niagara Falls: Ion Emission and
Sonoluminescence
Thomas
V. Prevenslik
Consultant
11 F,
Greenburg Court
Discovery
Bay, Hong Kong
Abstract
Over
100 years ago, Lenard explained waterfall electricity, a phenomenon
described
as the breakup of waterfall drops into fine particles that carry
negative
charge, the larger particles positive charges. Since then,
waterfall
electricity has been of interest to researchers, and is of
special
interest as this ESA Conference is held at Brock University near
Niagara
Falls, Ontario. Ion emission from waterfalls is proposed related to
the
phenomenon of sonoluminescence (SL). SL is usually described by the
emission
of visible (VIS) photons from bubbles in liquid , but is also
known
to dissociate molecules. It is
therefore not unreasonable to
postulate
the source of ion emission from waterfalls to be and ions
produced
as bubbles nucleate in drops at the splash. In the Planck theory
of
SL, the source of SL is the electromagnetic radiation (EMR) at
frequencies
from the ultraviolet (UV) to soft X-rays where liquid is
strongly
absorptive (and emissive). The EMR is accessed in bubble
nucleation
by cavity quantum electrodynamics (QED) as frequencies less than
the
bubble EM resonant frequency are inhibited from the bubble. Since the
bubble
EM resonance at nucleation occurs at soft X-ray frequencies, the
Planck
energy of EMR from soft X-rays to the UV that existed before
nucleation
is inhibited from the space after nucleation. The inhibited EMR
concentrates
at the bubble wall and has sufficient Planck energy to
dissociate
the surface molecules into and
ions. In this way, waterfall
electricity
is produced as the bubbles in the splash burst and the ions are
discharged
into the air. Consistent with the Lenard effect, the negative
charge
in the air near waterfalls, Niagara Falls in particular, is proposed
to
be ions that cluster with and
molecules; whereas, the positive charge
is the ions that cluster to molecules and remain near the splash.
Some Basic Phenomena of Water Boules
J.
Ahern and W. Balachandran
Department
of Systems Engineering
Brunel
University
Uxbridge,
Middlesex UB8 3PH, United Kingdom
email:
empgjca@brunel.ac.uk
Abstract
The
splashing of water from a fountain, drips falling into a damp steel
sink,
or the slow emergence of drops of pure liquid during filtration, will
sometimes
give rise to small drops called boules, typically in the range
2-5
mm in diameter, which careen briefly on a cushion of vapour above the
bulk
liquid below, before being absorbed into it. The phenomenon has
received
relatively little attention, and has some interesting electrical
events
associated with it.
A
brief review of the phenomenological literature is given. This is
followed
by a description of two methods by which boules may be produced in
the
laboratory with fair reliability. Finally, some experimental results
are
given. In the initial experiments the electric field-strength to
inhibit
the formation of boules was measured, and found to be in good
conformity
with that previously reported. This was followed by a series of
measurements
of the charge transferred by boules, and was found to be in
the
order of C for boules of some 3.5 mm
diameter. The second series of
experiments
began the investigation of the electrical events associated
with
drop coalescence, with a view to possibly shedding some light on the
mechanism
of charge transfer in boules themselves. Work is continuing to
gain
a greater understanding of the mechanism of the charge transfer
processes.
An ESD Solution with Cascode Structure for
Deep-Submicron IC Technology
Howard
Tang, S. S. Chen, Scott Liu, M. T. Lee, C. H. Liu,
M. C.
Wang, and L. C. Hsia
Device
Engineering Dept.
Technology
and Process Development Division
United
Microelectronics Corporation
No.
3, Li-Hsin Rd. 2, Science-Based Industrial Park
Hsin-Chu
City, Taiwan, R. O. C
E-mail:
howard_tang@umc.com.tw
Abstract
In
this paper, we will propose an ESD solution with cascode structure for
deep-submicron
IC technology to enhance its ESD robustness. Using the added
boron
implantation (PESD implantation) at the drain side of the stacked
NMOS,
the long-base parasitic NPN bipolar in the cascode NMOS structure can
be easily
triggered by the zener breakdown mechanism at the drain side
under
ESD stress conditions. Based on the test results, this method
provides
a significant improvement inthe cascode ESD performance.
Different Electrostatic Methods for Making
Electret Filters
Peter
P. Tsai1, Heidi Schreuder-Gibson2 and Phillip Gibson2
1Textiles
and Nonwovens Development Center (TANDEC)
The
University of Tennessee
Knoxville,
TN
fax:
(865) 974-3580, e-mail: ppytsai@utk.edu
2U.
S. Army Soldier Systems Command
Natick
Research, Development and Engineering Center
Introduction
Fibrous
materials used for filter media take the advantages of high
filtration
efficiency (FE) and low air resistance. Electrostatic charging
of
the media improves their FE by the electrostatic attraction of particles
without
the increase of pressure drop [1]. Three techniques, electrostatic
spinning
(ES) [2], corona charging [3] and tribocharging [4], are used to
make
and/or to charge the fibers or the fabrics. This paper will compare
the
FE and the surface charge potential of these three techniques. Their
processes
of making the media will be addressed and the media properties
will
be presented.
Electrostatic Micromirrors for
Subaperturing in an Adaptive Optics System
Mark
N. Horenstein1, Seth Pappas, Asaf Fishov, and Thomas G. Bifano2
1Department
of Electrical and Computer Engineering
2Department
of Manufacturing Engineering
Boston
University
44
Cummington St., Boston, MA 02215
Tel:
617-353-9052 Fax: 617-353-6440
Email:
mnh@bu.edu
Wavefront
sensors are used in many applications involving medical
diagnostics,
terrestrial imaging, target recognition, laser tracking, and
astronomical
observations. Under ideal conditions, the light emanating from
a
source image arrives as a series of uniform wave fronts that have the
local
structure of a plane wave at the image receiving device. In a
practical
situation, the latter could be a camera lens aperture, a
photographic
plate, the human eye, or a laser sensor. In situations where
light
from the image passes through a distorting medium, the light will no
longer
arrive as a local plane wave but rather as a non-planar, or
"aberrated"
wavefront. A wavefront sensor can help determine the degree of
distortion
in the aberrated wave. If the distorted wavefront is modeled as
a
series of connected, piecewise-linear planar wavefront segments, then the
sensor
can provide information about the degree to which the aberrated
wavefront
departs from an ideal plane wave.
Such
a sensor is extremely useful in systems employing adaptive optics. In
an
adaptive optics (AO) system, information from the wavefront sensor is
passed
to an image correction device that typically includes one or more
deformable
mirrors. The latter act to redirect the incoming wave, sector by
sector,
until it regains the shape of an undistorted, regular plane wave.
One
traditional form of wavefront sensor is the commercially available
Hartmann
device, an array of tiny lenslets that each intercept one sector
of
the incoming wavefront. Each lenslet of a Hartmann device produces its
own
focused spot on the Hartmann image plane. If the incoming wave is
regular
and planar, the Hartmann sensor will produce an evenly spaced array
of
spots. If, on the other hand, the wavefront is distorted, then the spots
produced
by the Hartmann lenslets will be displaced from their normal
positions.
In an AO system, spot displacement can be detected by a
charge-coupled
imaging device (CCD), similar to what one would find inside
a
standard video camera.
A deformable
mirror is a device whose reflected surface can be altered,
sector
by sector, to attain a slope that departs from its otherwise
perfectly
planar surface. In an adaptive optics system, the information
derived
from the Hartmann sensor is used to drive the elements of a
deformable
mirror placed in the optical pathway. The deformable mirror
changes
the direction of propagation each aberrant sector of the incoming
image
until the wavefront of the entire image again resembles a plane wave.
The
aberrant wavefront sectors are redirected to their proper directions,
thereby
"undistorting" the distorted image. One classic (non-electrostatic)
example
of a deformable mirror is the correction mirror that was placed inside the
Hubble telescope approximately two years after its initial launch. This fixed,
deformed mirror applies "reverse distortion" to the image reflected
off of Hubble's flawed, primary mirror.
Unlike
the large, fixed deformable mirror placed inside the Hubble, or
likewise
the "fun-house" mirrors that one finds in an amusement park,
modern
deformable mirrors are small (1 cm) and lightweight (grams), and are
typically
activated by electrostatic forces. They can be distorted at
mechanical
frequencies approaching 10 kHz. This feature makes possible
real-time,
electrostatic-activated image correction in situations where the
distortion
changes with time. Examples of the latter include terrestrial
imaging
through hot desert air, astronomical imaging through the earth's
atmosphere,
medical imaging through moving airways or blood vessels, and
point-to-point
laser communications through a smoke-filled environment.
Real-time
image correction with a conventional Hartmann sensor and
deformable
mirror requires complex digital signal processing. An
analog-to-digital
(A/D) converter must first digitize the pixel images from
the
CCD array. A dedicated computer or digital signal processing (DSP) chip
must
then decode the digitized data to determine the positions of the
Hartmann
spots, execute a control algorithm, and apply electrostatic
correction
signals via a digital-to-analog (D/A) converter and high-voltage
amplifier
to the elements of the deformable mirror. This process is
computer
intensive, electronics intensive, very time consuming., and often
the
factor most responsible for limiting process bandwidth in adaptive
optics.
This
paper proposes a novel way to perform sectored wavefront sensing
without
the use of a Hartmann sensor, a DSP chip, computer, or CCD. The
Hartmann
lenslet array is instead replaced with a binary-actuated,
electrostatic
digital-mirror device (DMD) and a single, position-sensitive
spot
detector. The CCD, analog-to-digital converter, and computer are
replaced
with a simple, robust, analog electronic circuit and high-voltage
amplifier
made from simple, off-the-shelf parts. With these components
alone,
sectored wavefront sensing can be performed without any digital
image
processing or Hartmann device. The segments of a correcting
deformable
mirror can instead be controlled directly from the output of the
position-sensitive
spot detector.
This
paper also discusses the features of the binary-mode electrostatic
digital
mirror device (DMD) used in our experiments. The DMD is an array of
electrostatically-actuated
micro-mirrors each capable of being driven into
one
of two positions, or bistable states. Unlike the sectors of a
deformable
mirror, which are a continuously variable, analog devices, the
pixels
of the DMD can reflect light in one of two preset directions only.
The
DMD is made using low-temperature, micro-electromechanical (MEMS)
fabrication
technology. The physics and fabrications methods of the digital
mirror
device elements are discussed in detail.
Evolution of Streaming Potentials in a Glass
Beads Bed in Terms of Temperature
P. O.
Grimaud and G. Touchard
LEA,
UMR 6609, Equipe Electrofluidodynamique
Boulevard
Marie et Pierre Curie, Teleport 2, BP 30179
86962
Futuroscope-Chasseneuil, France
Introduction
Phenomenon
of self-potential is nowadays of greater and greater interest in
geophysics
as it finds utility in various environmental fields such as
evaluation
of volcanic and seismic risks or hydrorheology.
It is
well known that motion of fluid inside a porous medium generates
creation
of streaming potentials.
Considering
a porous medium inside of which a fluid is moving, number of
studies
have shown correlations between streaming potential and various
parameters
characteristic of the medium, but it always seems to be
independent
of the temperature of the medium.
However,
explanation of this last observation never has been well explained.
This
is the reason why the aim of our work first consists to show
theoretically
the non-dependence of streaming potential with temperature,
then
to confirm it with an experimental study.