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.

 

Accudep?-A Revolutionary Process Technology for Manufacturing of

Pharmaceuticals

M. Kashef, S. Chrai, A. Katdare, R. Murari, G. Santonastaso

Delsys Pharmaceutical Corp.

Princeton, NJ

 

Accudep? 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. Accudep? technology replaces

all these steps with single electrostatic deposition process equipment and

eliminates most of the inactive excipients.

In Accudep? 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.

 

Accudep? 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 Accudep?

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 Accudep? process.

Several pharmaceutical powders have been characterized and successfully

deposited using Accudep? 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 Accudep? 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.