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June 23 - 26, 1998
Stanford University
Palo Alto, California

A bound copy of these Proceedings in their entirely can be obtained from Laplacian Press:

Contents

Preface

Fluids

Static Electrification in Power Transformers: Chemical Modeling of the Charge Transfer at the Oil-Pressboard Interface; O. Moreau, F. Augier, and G. Touchard

Streaming Current Generated by a Deionized Water Flow through Glass Capillaries of Different Radii; Thierry Paillat, Gerrard Touchard, Eric Moreau

Electro kinetic Phenomena in Microporous Media of Different Pore Sizes; Eric Moreau, Thierry Paillat and Gerard Touchard

Electrostatics of Fuel System for Automobile; Hironori Ueda and Takayuki Kato

Influence of Cathodic Protection of Soil-Buried Steel Pipelines on Oil-Flow Electrification; A. Metwally

The Effect of Polarity on the EHD Surface Waves of Dielectric Oil Thin Films Generated by Wire-Plate Barrier Discharges;
K Urashima, J. S. Chang, and G. Touchard

Electrostatic Field Aspect in the Theory of the Corona-Induced Solitary EHD Wave on a Dielectric-Backed Oil Film; T. S. Lee

Inlet Quality Effects on Horizontal Convective Boiling under the Electrohydrodynamic (EHD) Effect; C. Norris, J. S. Cotton, M Shoukri, T. Smith-Pollard, and J.-S. Chang

Preliminary Kerr Electrooptic Field Mapping Measurements in Propylene Carbonate Using Point-Plane Electrodes;
T. J. Gung, A. Ustundag, and M. Zahn

Liquids and Charge Control

Rotational Motion of Water Ligament Drawn by Electrostatic Force; K Asano and K Yatsuzaka

Multiple-Ring Structure in the Wake of a Corona Initiated Surface Wave on an Oil Film; Thao Pham and T. S. Lee

Evidence Showing the Wave Nature of the Mechanism for Passive Surface Charge Elimination; T. S. Lee

Development of the Charge Flux Equation Using the Contiguous Collision Averaging Method; Albert E. Seaver

A Study of ESD Damage To Thin Film Disks; Al Wallash and Harlan Snyder

Development of Vibrating Measurement Apparatus for Minimum Ignition Energy for Powder; W. L. Cheung, T. Kodama and M. Yamaguma

General Characteristics of a Newly Developed Bipolar Static Charge Eliminator; Y. Tabata, T. Kodama, W. L. Cheung and N. Nomura

Triboelectrification of Rock Crystal and Metal; Hisashi Shio

Electron Traps and Charging Characteristics of Polyethylene; Yuji Murata and Isao Hiyoshi

Development and Applications of Multi-Wavelength Interdigital Dielectrometry Sensors and Parameter Estimation Algorithms; A. V. Mamishev, Y. Du, B. C. Lesieutre, and M. Zahn

Measurements and Hazards

Measurement of Surface Conductivity in Dielectric Liquid; Yoshiyuki Matsubara

Sensitivity of a Vibrating Electrode Type Field Meter Driven at Ultrasonic Frequency; Mitsuru Matsui, Koichi Fujibayashi, Go Matsuaka and Norio Murasaki

Ionic Mobility Measurement in the High Temperature Atmosphere; Koichi Fujibayashi, Mitsuru Matsui, Hiroaki Kuroki and Norio Murasaki

Development of Conductive Glass-Lined Equipment Preventing Accumulation of Static Charge; Yoshihiro lizawa, Takashi Kawashima, and Tsutomu Kodama

Trial of Electrostatic Safety Evaluation for Pneumatic Powder Transport; Tsutomu Kodama, Konjiro Nishimura, Hideo Wada, and Satoshi Yokoyama

Computational Assessment of Electrostatic Hazards in a Vessel During the Filling of Charged Powder Particles; Atsushi Ohsawa

A Peculiar Electrification of Polyester Fibers and its Influence on Spinning Processes; Pellumb G. Berberi

Charge Decay in Thin Layers of Powder Paints; Toshihiro Ogiwara, Fumio Nakayama and Kazuo Ikezaki

Applications

Electrophoresis in a Plateout Cell; F. J. Wang, G. A. Domoto, H. R. Till, and John F. Knapp

Some Electrostatic Design Issues for a Thermal Receiver; Mark C. Zaretsky

The Influence of Paper Upon Sticking of Transparency Sheets; Humphrey Wong

Production of Ultra-Uniformly-Sized Silica Particles by Applying AC Superimposed on DC Voltage; Masayuki Sato, Hisashi Takahashi, Masashi Awatsu, and Takayuki Ohshima

Fabrication of Functional Polymer Thin Films by UV Laser Ablation; Tetsuji Oda and Masashi Yamada

Antistatic Process of Dielectric Thin Films using Low Pressure Discharge Plasma; Kazanori Takashima and Tetsuji Oda

Rotating Electrostatic Chuck Based on Corona Charging and Discharging; Mark N. Horenstein

Real Time Optical Correction Using Electrostatically Actuated MEMS Devices; Mark N. Horenstein, Seth Pappas, Julie Perreault, Thomas C. Bifano, and Raji Krishnamoorthy Mali

AC Electrostatic Levitation; Ju Jin and T. C. Yih

Electrostatic Separation of Industrial Waste Plastics for Recycling; C. S. P. Castle, 1. 1. Inculet and J. D. Brown

Discharges and Chemistry

Digestion of Nucleic Acid Molecules in Pulsed Electric Field and Its Release from Recombinant Escherichia Coli; Takayuki Ohshima, Takahiro Ono, and Masayuki Sato

Manipulation of DNA Molecules by Local Temperature Control; Ken Hirano, Shunichi Matsuura, Shinji Katsura, and Akira Mizano

Hysteresis, Self-Sustained Oscillations and Chaos in Space Charge Limited Currents; Y. N. Cartstein and P. S. Ramesh

Control of Flow Stabilized Positive Corona Discharge Modes and NO Removal Characteristics in Dry Air by C02 Injections; K Yan, T. Yamamoto, S. Kanazawa, T. Ohhubo, Y. Nomoto, and J. S. Chang

Corona Discharge Occurring at a Grounded Rod Electrode in a Charged Particle Cloud; T. Sugimoto, S. Doi, and Y. Higashiyama

Modeling Of Dry Air Chemistry In A Coaxial Wire-Pipe Negative Corona Discharge; J. S. Chang and A. Kwan

Performance evaluation of discharge plasma for DeNOx/DeSOx; Hyun Ha Kim, Craciela Prieto, Shinji Katsura, Akira Mizano

The Dilution Effect with Rare Gases for Direct Methanol Synthesis from Methane using Non-Thermal Plasma; Mamoru Okamoto, Zhenzhou Su, Shinji Katsura and Akira Mizuno

Preface

Four years ago the Electrostatics Society of America and the Institute of Electrostatics Japan embarked on a new era of international cooperation. Their first joint symposium was held at Stanford University in June, 1994, at the regular time of the ESA Annual Meeting. The meeting was very well received, with many papers contributed from Japan and North America, as well as other areas around the world. As a result, both organizations agreed that a regular joint meeting should be arranged every two years. In October, 1996, a second successful meeting was held in Tokyo, in conjunction with the annual meeting of the IEJ. This year, the joint meeting returns to California, and again promises to be one of the most important events in electrostatics for the year.

Another innovation from the first joint meeting was the publication of a proceedings volume. Until then, there was no permanent record of the many interesting presentations made at the annual ESA meeting. Publication of the proceedings of the joint symposium led the ESA to decide on the annual publications of a proceedings volume, a policy already followed by the IEJ. Now, four years later, the ESA proceedings are regularly cited in journal articles dealing with electrostatics, an indication of its acceptance by the scientific community. The present volume is the largest ESA proceedings to date, with over 400 pages of technical articles covering applications of electrostatics to numerous areas, including air quality control, color printers, protection of electronics and industrial facilities, genetic engineering, and landmine detection. In addition, there are numerous contributions on fundamental aspects and measurement techniques, both of which are essential to continued progress in practical applications.

While the printed record is important, the real benefits of the symposium come to those who attend and have the chance to meet people with a kindred interest in electrostatics from all over the world. In keeping with the tradition of "The Friendly Society," there is always some time in the program for attendees to report some recent interesting work. Numerous breaks and social activities give everyone the chance to renew acquaintances and meet new friends. We are grateful to Calvin Quate for making it possible to meet here, and we hope that you find this symposium useful for your work, and a pleasure for you personally.

Joseph M. Crowley

1998 Conference Chairman

Static Electrification in Power Transformers: Chemical Modeling of the Charge Transfer at the Oil-Pressboard Interface

O. Moreaul, F. Augier, and G. Touchard

Electricite de France
Direction des Etudes et Recherches
Service Mate'riel Electrique
I av. Ge'ne'ral de Gaulle
92141 Clamard, France

Universite'de Poitiers
Laboratoire de Physique et Me'canique des Fluides
40 avenue du Recteur Pineau
86022 Poitiers France

Abstract

Static electrification has been suspected to be responsible of power transformers incidents when damage surveys revealed some evidences of electrical discharges (electric "tree" paths, "worm holes," presence of carbon...) on inner pressboards. This physiochemical phenomena leads, on one hand, to a space charge in the oil which can relax in contact with grounded metallic walls and on the other hand to a space charge in the pressboard which can accumulate depending on the leakage paths. Although all the parameters of influence seem to be now clearly identified, their critical combination still remains unknown. As part of the research program of Electricite de France, a numerical modeling with an extended version of the computational fluid dynamic software ESTET, developed at the R&D center of Electricite de France (EDF), associated to experiments at the University of Poitiers, has been performed to derive two chemical approaches to the phenomenon of charge generation which fit the experimental data in term of flow geometries and velocity dependence. The aim of these investigations is to predict, on a transformer scale, some failure contexts which might be encountered in operating devices.

Thierry Paillat, Gerard Touchard, Eric Moreau

Laboratoire d 'etude Aerodynamique
UMR 6609 CNRS, Universite'de Poitiers
40 Avenue du Recteur Pineau
86022 Poitiers, France

Abstract

This paper deals with experimental measurements of streaming current generated by a flow of deionized water through glass capillaries. The characteristic values of electrokinetic phenomena (space charge density at the solid/liquid interface Pw and zeta potential (~) are calculated from Touchard's model. The measurements with capillary of different radius show that the space charge density at the interface does not depend on fluid flow channel radius but only on the chemical nature of the liquid.

Eric Moreau, Thierry Paillat and Gerard Touchard

Laboratoire d 'Etudes Aerodynamiques
UMR 6609 CNRS, Universite'de Poitiers
40 avenue du Recteur Pineau
86022 Poitiers, France

Abstract

This paper deals with streaming current generated by water flow through fritted glasses of different pore sizes. First, image analysis allows to characterize the porous medium geometry and then to propose a morphological model. With this model and the theoretical knowledge of the electric double layer at the solid-liquid interface, and the streaming current measurements, the space charge density Pw at the wall and the zeta potential (~) are determined. In the case of water, as shown with others liquid, it seems that Pw does not depend on the pore size.

I. A. Metwally

Electrical Engineering Department
Mansoura University
Mansoura, Egypt 35516

Abstract

Both cathodic and anodic protection attempt to employ electrochemical measures to reduce the corrosion rate of metals by external polarization. In this paper, a synthetic closed cycle is adapted to simulate the soil-buried/water-immersed steel pipeline, where a fresh transformer oil type Wewco-C(tm) is pumped in a steel pipe which is electrically isolated from the rest of the cycle. The latter is fixed coaxially through a plastic cylindrical container filled with distilled water; where the DC voltage is applied across it and a water-immersed brass electrode. Many factors are experimentally examined to show their effects on the electrostatic charging tendency (ECT) of flowing oil. The ECT of oil is quantified by measuring the streaming current of the flowing oil from an isolated and electrostatically screened tank. These factors are oil velocity and temperature, magnitude and polarity of the applied voltage to the pipe, and magnitude of the external magnetic field. The results reveal that the ECT of oil is highly dependent on both magnitude and polarity of the protection current. The higher the protection current the higher is ECT of oil. Cathodic protection gives higher ECT of the flowing oil than that for anodic protection. Also, the ECT of oil is enhanced by oil velocity, oil temperature, and/or the external magnetic field. A derived formula for the streaming current is also presented.

K. Urashima, J. S. Chang, and G. Touchard

Department of Engineering Physics
McMaster University
Hamilton, Ontario, Canada LOS 4MI
Telephone: (905)525-9140, ext. 24924
Fax: (905)527-5222
email: changj@mcmaster.ca

Universite de Poitiers
Poitiers, France

An experimental investigation has been conducted to study the effect of polarity on the EHD (electrohydrodynamically) induced surface wave phenomena on the surface of dielectric diesel oil thin films under wire-plate barrier discharges. Diesel oil used is dielectric constant es = 2.2 and conductivity 6 = 5xlO-5 pS/m and positive DC (on/off) high voltage was imposed on the plate electrode. Experiments are conducted for the applied voltage from O to 29 kV. The experimental results show that the oil film wire and an expanding depression surface wave initiated with short time delay when voltage is off to on under positive polarity cases. After another short delay, hydraulic jump imploding wave is also generated. For voltage on to off in negative polarity case, T-L type expanding wave is generated with short delay time and then imploding wave is formed behind T-L type waves. The wave propagation speed is always higher in the gravitation direction and the effect of polarity on the propagation speed will be discussed in detail.

T. S. Lee

Electrical Engineering Department
University of Minnesota
Minneapolis, MN 55455
ph: 612-625-2346fax: 612-6254583
email: tslee@ee.ur~m.edu

Abstract

The experimental evidence as well as general characterizations of a class of soliton wave-like phenomena was reported earlier. Crucial evolutionary details of such an event have not been satisfactorily explained. It is submitted that both electrostatics and electrohydrodynamics play important underlying physical roles. In this work, a theory restricted to purely electrostatic considerations is proposed. Ensuing analyses show the importance of the existence of a saddle-point in the field outside the film. A physical explanation behind the wave phenomenon is indicated.

C. Norris, J. S. Cotton, M. Shoukri,
T. Smith-Pollard2, and J.-S. Chang3

Department of Mechanical Engineering
McMaster University
Hamilton, Ontario, Canada.

2Long Manufacturing Ltd.
Oakrille, Ontario, Canada.

3Department of Engineering Physics
McMaster University
Hamilton, Ontario, Canada.

Abstract

Experiments have been performed to demonstrate the el: feet of the electrohydrodynamic (EHD) technique of heat transfer enhancement for single component evaporation in a smooth, horizontal, indirectly heated tube with a concentric cylindrical electrode. Experiments were conducted for mass fluxes of the working fluid, R-134a, ranging from 100-250 kg/m2s, inlet qualities from 20-50% and applied voltages of 0 to 10 kV for an annular gap of 3.87 mm, with an inner-to-outer diameter ratio of 0.29. The results show that: ( I ) Measurements of the tube surface temperatures demonstrate that the application of the electric field affected the flow regime; (2) Plots of average surface excess temperature at specified axial locations show that the application of an electric field reduces the length to dryout; (3) Temperature waveforms show the response of the thermocouples, and observations are made with respect to the amount of liquid or vapor in contact with the surface at that point, (4) An increase in inlet quality also reduces the length to dryout since flow exists in the droplet or mist regime in high quality regions; and (5) The effect of EHD on flow regime is seen to have a significant effect on heat flux. The application of an electric field reduced the heat flux in all cases. An increase in inlet quality reduced the heat flux.

T. J. Gung, A. Ustundag, and M. Zahn

Massachusetts Institute of Technology
Department of Electrical Engineering and Computer Science
Laboratory for Electromagnetic and Electronic Systems
Cambridge, MA 02139 USA

Abstract

Propylene carbonate is used in Kerr electrooptic field mapping measurements because of its nontoxic chemical nature and very high Kerr constant. We describe the experimental design and chemical purification procedure that minimizes reactions with the electrodes and removes particles and moisture. We measure the optical characteristic parameters using the AC modulation method with point-plane electrodes. The "onion peeling" method is then used to recover the radial and axial components of the electric field which are compared to the theoretical space charge free solutions.

Rotational Motion of Water
Ligament Drawn by Electrostatic
Force

K. Asano and K. Yatsuzuka

Yamagata University
Dept. Electrical and Information Engineering
Yonezawa, Yamagata-ken 992-8510, Japan
Phone: +81-238-26-3260 Fax: +81 ~238-26-3264
email: asano @ eie.yz.yamagata-u.ac.jp

Abstract

Electrostatic spraying is useful to produce fine charged droplets or mist with a simple apparatus. It has long been believed that the cone-shape spraying is produced directly from the breakup of a column. Recently it is shown that column shows kinking motion and then breaks up into droplets. In this report, fundamental characteristics of electrostatic spraying with a syringe needle and a plane electrode configuration are presented, including the sequential pictures of the droplet formation process which are taken with a high speed video camera. It revealed that the water column ejected from a needle electrode is whirling spirally and then breaks up into tiny droplets. The charged droplets spread out downwards with cone shape. The speed of whirling motion is accelerated with the applied voltage. The size of charged droplets becomes smaller when the applied voltage increases. The relationship between the current due to charged droplets and the applied voltage is also measured. The light emission and audible noise are observed at the tip of whirling column.

Thao Pham and T. S. Lee

Electrical Engineering Department
University of Minnesota
Minneapolis, MN55455
ph: (612) 625-2346fax: (612) 625-4583
email: tslee@ee.umn.edu

Abstract

Under some combinations of physical conditions, discreet ring signatures may emerge in the wake interior [Lee and Tran 1995], following the passage of the wavefront of an inverse-corona excited surface wave on an dielectric-backed oil film. They appear stationary in position and well sustained in time. Comparison shows that they are in intimate association with the pulse-bunching phenomenon which might take place in the related corona current trace.

T. S. Lee

Electrical Engineering Department
University of Minnesota
Minneapolis, MN 55455
ph: (612) 625-2346 fax: (612) 625-4583
entail: tslee@ee.umn.edu

Abstract

On the surface of a charged, ground-backed polymer layer, experimental evidence is reported of the wave nature inherent in the phenomenon of passive electrostatic surface charge elimination through the time-resolved physical process of induced corona neutralization.

Albert E. Seaver

3M Engineering Systems and Technology
3M Center, Bldg. 518-1 01
St. Paul, MN55144-1000
Ph: (612) 733-8629 Fax: (612) 736-3122
email: aeseaver@mmm.com

Abstract

In gases an electron-neutral collision averaging method which gives the Langevin equation is usually used to determine the average velocity of the electrons. Diffusion effects are then added to allow the computation of the total charge flux. In this paper the concept behind the contiguous-collision-averaging (CCA) method-which can be used to determine the average velocity of the free charges located at any point in a solid, liquid or gas-is developed wherein the diffusion and thermal effects are included within the averaging. Then the CCA method is initially used to determine the average velocity of a single free charge species when forces due to thermal and charge gradients along with a constant electrical force are all acting on the species. The result leads to a general charge flux equation for the species when magnetic field effects are ignored. In the development of the charge flux equation the electrical conductivity, mobility, diffusion coefficient and thermophoresis coefficient are explicitly and clearly defined and the relationships between each of these terms are presented. Next the assumptions required for the charge flux equation to reduce to Ohm's Law are presented and discussed. Finally, the charge flux equation for a material possessing multiple species of charge is developed. The CCA method is an approach that offers intuitive simplicity and an easy way to understand the main physics involved in the transport of charge.

A Study of ESD Damage To Thin
Film Disks

Al Wallash 1 and Harlan Snyder 2

1 Quantum Corporation
500 McCarthy Blvd,
Milpitas, CA 95035
(408) 324-7539
awallash @ qntm. com

2Technical Consulting Associates
P. O. Box 2925
Saratoga, CA 95070
(408) 257-8811
hsayder@svpal.org

Abstract

In the disk file industry ESD studies have focused on the traditional active device failures, particularly with various CMOS technologies, and the recently introduced MR (magnetoresistive) read elements. However it has been known for some time that the disk surface itself may also be damaged by ESD. This study was conducted to demonstrate that at relatively low potentials, as might be seen in manufacturing, the thin film magnetic surface will suffer catastrophic damage in metal to metal discharge. The damage is easily quantifiable by optical microscopy, optical profilometry, and atomic force microscopy.

W. L. Cheung, T. Kodama and M. Yamaguma

Physical Engineering Safety Research Division
National Institute of Industrial Safety
1 4-6 Umezono, Kiyose-shi
Tokyo 204, Japan
Phone: +81 424 914512 email: kodama@res.anken.go.jp
Fax: +81 424 91 7846 web: www.res.anken.go.jp

Abstract

This paper describes the development of a vibrating minimum ignition energy (MIE) measurement system. Powder dispersion is based on imposing 50 Hz vibrations to a U-shape wire mesh of 1lm in size. The resulting powder cloud is flat and its concentration can be controlled manually by varying the vibration magnitude. Experimental work based on Lycopodium powder have lead to important factors such as the ignition spark gap and parameters related to the design of the powder dispersion mechanism to be determined. A discussion on the results together with a visual presentation of the operation of the system are presented.

Y. Tabatai, T. Kodama1, W. L. Cheungi and N. Nomura2

I National Institute of Industrial Safety, Ministry of Labour
1 4-6, Umezono, Kiyose, Tokyo 204 Japan
Phone: +81 424-91-4512 Fax: +81 424-91-7846
Email: tabata@res.anken.go.jp

2Kasuga Denki Inc.
2-16, Higashi-kamata, Ohta-ku, Tokyo 144 Japan
Phone: +81-3-3733-6627 Fax: +81-3-3738-6521

Abstract

A new bipolar static charge eliminator suitable for neutralizing charged films and webs traveling at high speed is described. The device consists of an in-line array of resistance coupled needle electrodes which are driven simultaneously and alternately into positive and negative corona discharges by unequal voltages from an integrated bipolar HV power supply. A smooth residual surface potential profile measured several hundred volts in magnitude can normally be attained after neutralization. The amount of ozone and electromagnetic noise being produced were found to be insignificant. Finally, the discharges drawn by approaching an unearthed object to the electrodes were found to be non-incendiary.

Hisashi Shio

Department of Physics
Hokkaido University of Education 2-34
Iwamizovva, Japan

Abstract

In order to make clear charging mechanism of ice, using rock crystal, silica, quartz and metal triboelectrification was investigated. As a result, polarity of these charging was dependent on crystal anisotropy, namely, crystallographic orientation of rubbed surface, about many kinds of metals the polarity of charging was controlled magnitude of work function of these metal.

Electron Traps and Charging
Characteristics of Polyethylene

Yuji Murata and Isao Hiyoshi

Department of Electrical Engineering
Faculty of Science & Technology,
Science University of Tokyo

Ncchu Inc.

Abstract

The information of difference in electron traps of different density polyethylene was obtained from photoemission data measured using samples exposed to an electron shower. The higher density polyethylene has higher density of electron traps and tends to charge much negatively.

A. V. Mamishev, Y. Du, B. C. Lesieutre, and M. Zahn

Laboratory for Electromagnetic and Electronic Systems
Department of Electrical Engineering and Computer Science
Massachusetts Institute of Technology
Cambridge, MA 02139, USA

Abstract

Recent advances in the field of interdigital co- k (frequency-wavenumber) dielectrometry are described. The paper offers an overview of several applications of this technology developed during the last few years. Interdigital ~o- k dielectrometry offers the ability to non-destructively measure from one side dielectric permittivity, conductivity and related physical properties distributed spatially throughout the volume of dielectric materials. A separate mapping may be required to translate the distribution of the complex dielectric permittivity into the distribution of other properties, which include moisture concentration, impurity concentration, density, porosity, thickness of films, structural integrity, surface coatings, etc. As representative examples of applications of this technology, the results of the measurement of moisture diffusion into a 1.5 um thick oil free transformer pressboard are presented, followed by an illustrative case of spectroscopy-based landmine detection.

Measurement of Surface
Conductivity in Dielectric Liquid

Yoshiyuki Matsubara

National Research Institute of Fire and Disaster
3-14-1 Nakahara Mitaka-si, Tokyo 181-8663 Japan
phone (81) 422~4-8331 Fax: (81)-422-42-7719
email: matsu@fri.go.jp

Abstract

Theoretical studies revealed that charge leakage through surface conduction should play an important role during the transient relaxation process of surface potential within containers which are partially filled with charged oil. We prepared test equipment for the measurement of surface conductivity of oil, and conducted an experiment to determine the surface conductivity of kerosene whose rest conductivity was I pS/m. Results of the measurements say that the surface conductivity should be as small as I fS (10-ls S) or less. If the surface conductivity of rest kerosene is so small, variation of surface conductivity caused by the electrostatic charging might be taken into account, as is true for the case of exceedingly low bulk conductivity, when we construct theoretical models on the transient relaxation of surface potential.

Mitsuru Matsui, Koichi Fujibayashi Go Matsuoka and
Norio Murasaki

Department of Electrical and Electronic Engineering,
Tokyo University of Agriculture and Technology,
Nakamachi, Koganei-shi, Tokyo 184-8588, Japan
Phone: +81-42-388-7126 Fax: +81-42-385-6729
email: matsuim@cc.tuatac.jp

Abstract

Piezoelectric ceramic ultrasonic vibrators have been adopted to drive the induction electrode of vibrating electrode type field sensor and the sensitivity and its drive frequency dependence have been investigated. The sensitivity of the field sensor designed has been adequate to practical use for static charge measurement and increased with increasing drive frequency as well as vibrating amplitude. At the resonant frequency of the vibrator a large sensitivity has been obtained so that ultrasonic vibrator is available to diminish the size of field meter.

Koichi Fujibayashi, Mitsuru Matsui, Hiroaki Kuroki and
Norio Murasaki

Department of Electrical and Electronic Engineering,
Tokyo University of Agriculture and Technology,
Nakamachi, Koganei-shi, Tokyo 184 8588, Japan
Phone: +81 -42-388-7134 Fax: +81 -42-385-6729
email: fjb@cc.tuat.ac.jp

Abstract

The mobilities of ions generated corona discharge are measured at the temperature up to 420 •C in the atmospheric pressure air using a triple coaxial cylindrical electrode system and estimated applying Child's law concerning the space charge limited conduction current to V-l characteristics curves. The mobility has increased in relation to square root of the temperature, in the lower temperature range. In the higher temperature the mobility, especially of negative ions, has extremely increased with the temperature that suggests change of species of the ions and generation of secondary electrons.

Yoshihiro Ibiza 1, Takashi Kawashima 2 and
Tsutomu Kodama 2

l Ikebukuro Horo Kogyo Co., Ltd.
735 Shimotomi Tokorozawa Saitama 359 Japan
Tel: +81 429-42-1181 Fax: +81 429 42-8034

2 National Institute of Industrial Safety
1 4-6 Umezono Kiyose Tokyo 204-0024 Japan
Tel: +81-424-91 4512 Fax: +81-424-91-7846
email: kodama@res.anken.go.jp

Abstract

When a high resistivity of glass lined vessel is used for agitation of a two phase liquid system, which consists of high resistivity liquids and suspended substances like solid particles, a considerable amount of electrostatic charge can accumulate on the glass lining and cause consequently serious problems like breakage of the glass lining or explosion due to such electrostatic discharges. So, for the purpose of solving these problems, conductive glass lined equipment having not only antistatic performance, but also strong chemical and mechanical resistance have newly been developed. This paper describes the materials used and the antistatic characteristics of newly developed conductive glass lined equipment.

Tsutomu Kodama 1 , Koujiro Nishimura 2, Hideo Wada 2 and
Satoshi Yokoyama 3

National Institute of Industrial Safety, lilinistry of Labour
1-4-6 Umezono Kiyose-shi Tokyo 204 0024 Japan
Tel: +81-424-91-4512 Fax: +81-424-91-7846
email: kodama@res.anken.go.jp

2Kasuga Denki Co., Ltd.
2-16-18 Higashi-kamata Ohta-ku Tokyo 144 Japan
Tel: +81-3-3733-6627 Fax: +81-3-3733-6638

3Asahi Chemical Industry Co., Ltd.
2-1 Samejima Fuji-city Shizuaka-pref. 416 Japan
Tel: +81-545-62-2341 Fax: +81-545-62-2369

Abstract

For the purpose of preventing dust explosion caused by electrostatic discharges during pneumatic transportation, triads were conducted for electrostatic safety evaluations using air blow type field sensors. Experiments were carried out using full scale pneumatic transporting facility. A field sensor was mounted to a pipe wall in order to estimate the specific charge of powder within the pipe. It was also mounted to a silo wall for sensing electrostatic field strength inside the silo. Experimental results have shown such field sensors are applicable for safety evaluations when pneumatic transportation is concerned.

Atsushi Ohsawa

Physical Engineering Safety Research Division,
National Institute of Industrial Safety,
Umezono, Kiyose, Tokyo 204-0024, Japan
Phone +81424-91-4512 Fax +81 424-91-7846
Email: ohsawa@res.anken.go.jp

Abstract

Electrostatic hazards that may occur in a vessel during the filling of a charged powder have been estimated by using a particle-in-cell simulation. The motion of the charged particles and the electric field inside the vessel have been solved self-consistently. The particle size distribution of the powder has also been taken into account. Four powders, each having a log-normal size distribution have been used to investigate the dependence of particle size on hazards. The probability of incendiary discharges is assessed by calculating the local electric fields and electrostatic energies. The possibility of incendiary discharges on the top of the heap was demonstrated.

Pellumb G. Berberi

Department of Physics
The Polytechnic University of Tirana
Tirana Albania

Abstract

Humidity of the air is one of most important technological parameters in processing textile fibers. Among others it is very important when static electrification is considered. There are numerous evidences and it is widely accepted that static electrification diminishes with increasing relative humidity. A long term investigation of static electrification of PET fibers maklen 140m during spinning performance, evidences a peculiar alternating influence of relative humidity of the air on its static electrification. Existence of this alternating component is a clear evidence of structural modifications on the surface of PET fiber due to water vapor absorption which, in its side, leads to this peculiar modification of static electrification propensity of the fiber. A direct correlation is observed between static electrification and some of technological parameters.

Toshihiro Ogiwara, Fumio Nakayama and Kazuo Ikezaki

Department of Applied Physics and Physico-luformatics,
Faculh, of Science and Technology, Keio University
3-14-1, Hiyoshi, Kohoku-ku, Yokohama, 223-8522 Japan

Charge decay characteristics of powder beds of a commercial paint for electrostatic powder coating were examined by observing isothermal surface voltage decay and thermally stimulated current spectra. At 40 •C and relative humidity of 60%, the surface voltage V decreased with time t from the initial surface voltage VO in accordance with an empirical relation In (VO/V) o~ ~It which ~ well known to hold in powder systems. At higher temperatures of 45 and 5~, however, the surface voltage decay curves did not obey this empirical relation. By means of thermally stimulated current spectra for these samples, this disagreement was explained to be due to change in molecular aggregation state of this sample polymer at higher temperatures.

Electrophoresis in a Plateout Cell

F. J. Wang, G. A. Domoto, H. R. Till, and John F. Knapp

Xerox Corporation, Wilson Center for Research and Technology

Abstract

Liquid inks, suspensions of charged toner particles (pigmented resin) in nonconductive liquids, are used to tone latent images in liquid electrophotography. The charging of the liquid toner is established through acid-base chemistry [ I ]. Once chemical equilibrium is reached, there will exist multiple charged species of both polarities in the ink. The performance of liquid toning, given the ink and the toning process, is determined by the charge of the toner and the charge that is associated with other non-pigmented species. Hence, characterization of the liquid ink charging is crucial.

A technique, plateout [2], has been applied to measure these charging characteristics. Liquid toner, placed between two parallel electrodes, will be deposited on one electrode after application of electric fields. Other charged species, carrying either the same or opposite polarity, the so-called co-ions and counter-ions, will also move under field. Current measurement can be made as well as the visualization of the toner deposition process. Interesting deposition features have been observed and we explain them with the use of numerical modeling. The interpretation leads to theory that fast-moving co-ions and counter-ions can significantly change the plateout features.

In addition to the experimental and numerical results are the description of the numerical formulation, schemes, and verification against some analytical results. Note that the plateout cell is stationary and its toner deposition processes are significantly different from the toning processes in commercial electrophotographic systems, differentiated mostly by the fluid motions and the geometry. The ramifications in practical toning due to the fluid flow and geometry are discussed.

Mark C. Zaretsky

Eastman Kodak Company
Rochester, NY 14652 4325
Phone: (716)588-6351
Email: mcz@kodak.com

Abstract

Electrostatic charging of a thermal receiver was found to be the cause of transport problems in a thermal printer. Charging was a result of the dye transfer process and occurred upon separation of the receiver and donor material. Transport problems arose because highly charged receivers would stick to metal guides in the printer. Placement of an antistat layer on the back of the receiver resulted in a significant increase in charge level, causing the receiver to jam at elevated relative humidity (RH) conditions. Placement of an antistat layer on the face of the receiver resulted in a significant reduction in charge level, completely eliminating the transport problem for all RH conditions. It was hypothesized that the maximum charge level at separation appeared to be limited by ionization at the donor-receiver separation point and dependent upon the proximity of a ground potential to the back of the donor and receiver. A simple, one-dimensional electrostatic model was developed to evaluate this hypothesis and it provided good qualitative agreement with the observations and measurements of charge and transport performance.

Humphrey Wong

Surface Modification and Electrostatics Unit, MR&E, SGPC
Eastman Kodak Company
Rochester, NY 14652-4325

Abstract

The sticking of transparencies to one another within a stack is often observed to vary depending on a number of factors including time, RH, and the electrical properties of the sheets. Stickiness levels can range from being barely noticeable to levels that produce crackling as the sheets separate from one another, occasionally leaving even the neatest stack of transparencies in disarray. This talk describes how the interleaving of paper sheets between transparencies can influence the resulting stickiness of the stack. Both the discharging behavior and the charge state of the sheet surfaces are examined, and a mechanistic model is presented to explain the observed behavior.

Masayuki Sato, Hisashi Takahashi, Masashi Awatsu, and
Takayuki Ohshima

Department of Biological and Chemical Engineering
Gunma University,
1-5-1 Tenjin-cho, Kiryu, Gunma, 376-8515 Japan
Phone: +81-277-3~1468 email: mxsato@bce.gunma-u.ac. jp
Fax: +81-277-3(~1469 http://faculty.bce.gunma-u.ac.jp/mxsato/

Abstract:

Silica particles have been produced by means of agitation or by using a porous glass membrane to make a water-glass emulsion with subsequent solidification into silica particles through de-Na processes. Using these ordinary methods, the particles usually have a wide size distribution. The authors propose a new method to produce ultra-uniformly-sized silica particles by application of an electrostatic atomization and solidification method. The water-glass is dispersed into ultra uniformly-sized droplets by an applied AC superimposed on DC voltage, then collected in an alcohol solution to solidify the droplet surfaces by dehydration of water from the water-glass. Finally the droplets are converted into solid particles after Na is removed using a sulfuric acid solution. It was found that silica particles with a uniformity factor of 0.017 were produced by the proposed method. Droplet formation mechanism was also studied experimentally by comparing the video image at the moment of the liquid breakup and the wave shape of electric current flowing through the ground electrode.

Tetsuji Oda and Masashi Yamada

Dept. Electr. Eng.
The University of Tokyo
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 Japan
Phone+8l-3-3812-2111 ext. 6666 Fax+8l-3-5689~739
email: oda@ee.t.u-tokyo.ac.jp

Abstract

Excellent polymer films made of PTFE (polytetrafluoroeyhylene) were fabricated by using a UV laser (ArF excimer laser) ablation method. Main parameters tested were laser oscillation frequency, substrate temperature and laser power density. Film thickness fabricated is from a few nanometers to a few tens micrometers. An optimal laser power energy density at the target surface to make a good film was found to more 2 J/cm2. PTFE films made by laser ablation contains more fluorine than that made by vacuum evaporation. Existing of chemical bonding of {:F2on the surface of a new film manufactured by the laser ablation is confirmed.

Kazunori Takashima and Tetsuji Oda

Department of Electrical Engineering
School of Engineering
The University of Tokyo,
7-3-1, Hongo, Bunkyo-ku, Tokyo, 113 Japan

Abstract

By using space charge density distribution measurement and TSDC measurement, space and surface charge behavior of the corona-charged polypropylene (PP) and polyethylene (PE) thin film was studied. Effect of antistatic process using low pressure discharge plasma and charge elimination process dipping in city water was examined. In order to study the mechanisms of the antistatic process, the composition of the sample surface was analyzed by X-ray photoelectron spectroscopy.

It was observed that plasma surface processing enhanced the charge elimination performance for both PP and PE films. Charge accumulation in/on plasma processed PE films were much smaller than that of original ones. XPS analysis of those samples suggested the existence of carbonyl, carboxyl and amino groups on the surface of the plasma processed sample. Particularly a large amount of amino group was found on the surface of the sample processed in nitrogen.

Mark N. Horenstein

Dept. of Electrical and Computer Engineering
Boston University
8 Saint Mary's St., Boston, MA 02215
Phone: (617) 353-9052
email: mnh@bu.edu
Fax: (617) 353-6440

Abstract

This talk and demonstration describes the design and testing of an electrostatic chuck used to secure a metal disc to a conducting, rotating plate. The electrostatic chuck was designed for use in a compact-disc (CD) mastering system in which circular stamper plates are laser etched using a photoresist technique. The particular constraints of the problem require that the stamper plate, a thin, 0.5-mm thick, 20-cm diameter nickel-coated stainless-steel disc, be held firmly (to l-pm tolerance) to a chuck plate rotating at approximately 1800 rpm for up to two hours without extraneous physical contact. After processing, the disk must be readily removed using gravity only. In this way, physical distortion of the stamper disk and the risk of surface damage are substantially reduced. In the electrostatic system described here, an insulating sheet is placed between the stamper disk and the rotating, grounded chuck plate. The stamper disk is then charged via corona current, creating an electrostatic force that holds it against the chuck plate. After laser processing, the stamper disk is rapidly released by the application of an AC corona flux that neutralizes the accumulated charge.

Real Time Optical Correction
Using Electrostatically Actuated
MEMS Devices

Mark N. Horenstein, Seth Pappas , Julie Perreault,
Thomas G. Bifano2, and Raji Krishnamoorthy Mali2

Dept. of Electrical and Computer Engineering
Boston University
8 Saint Mary's St., Boston, MA 02215

2Dept. of Aerospace and Mechanical Engineering
Phone: (617) 353-9052 email: mnh@bu.edu Fax: (617) 353-6440

Abstract

This paper describes an optical correction system made from electrostatically actuated, surface machined micro-electromechanical (MEMS) mirrors. Such mirrors have applications in optical systems where they are used to correct wavefront aberrations and other image distortions. In our experiments, electrostatic actuators having a maximum surface-normal stroke distance of 2.5 pm control the individual orientations of each element in an array of 300-pm square mirror segments in the tip-tilt mode. Real time correction of random optical aberrations is demonstrated using a single mirror segment with four independently mounted corners and closed-loop feedback control.

Ju Jin and T. C. Yih

1ADE Corporation
9625 Southern Pine Blvd.
Charlotte, NC 28273

2Department of Mechanical Engineering
Florida International University
10555 West Flagler St., Miami, FL 33174
Phone. & Fax: 305-348-3140 email: yih@eng.fiu.edu

Abstract

This paper introduces the electrostatic levitation technique using tuned LC circuits. Presented are the following topics: basic system configuration, operation principle, dynamic instability, and applications. Its advantages and disadvantages are also discussed when compared with the servo-controlled DC electrostatic levitation technique.

G. S. P. Castle, I. I. Inculet, and J. D. Brown 2

Applied Electrostatics Research Center
University of Western Ontario
London, ON, N6A 5B9
Canada

2Plas-Sep Ltd.
95 Cumberland Cres.
London, ON, N5X I B7
Canada

Abstract

The authors describe some successful experiments for electrostatic separation of various two-component mixtures of waste plastics. Two methods of triboelectric charging of the plastics are described. One consists of a fluidized bed system with a central feeding tube. The second is a novel (patented) form of rotating tube charger. Separation takes place in an electrostatic separation tower equipped with a set of nine sampling bins at the bottom for collection of the components. Numerous experiments under various operating conditions have demonstrated the feasibility of obtaining extract contents in excess of 99% with recoveries of over 85% for single-pass operation. The rotating tube charger is preferred over the fluidized bed because of its simplicity and low energy requirements. Results are presented from an industrial scale version of the process which is capable of separating 1000 kg/hour of post-industrial plastic waste.

Digestion of Nucleic Acid
Molecules in Pulsed Electric Field.
and Its Release from
Recombinant Escherichia Coli

Takayuki Ohshima, Takahiro Ono, and Masayuki Sato

Department of Biological and Chemical Engineering
Faculty of Engineering, Cunma University
1-5-1 Tenjintyo, Kiryu, Gunma-ken 376-8515 Japan
tohshima@bce.gunma-u.ac.jp

Abstract

The influence of pulsed electric field (PEF) on chromosomal DNA, plasmid DNA, and RNA molecules was studied. It was conf irmed that chromosomal DNA and RNA were digested to smaller size or disappeared in PEF because of observations on agarose gel electrophoresis of nucleic acid molecules before and after PEF treatment. However, supercoiled form of plasmid DNA was relatively stable in electric conditions when other nucleic acid molecules containing linear and opened circle forms of plasmid DNA were digested. This phenomenon suggested that the digestion of nucleic acid molecules seemed to be one of the reasons of pulse sterilization. We also studied a release of nucleic acid molecules from recombinant E. cold in PEF to improve a method of plasmid DNA preparation. Although some kinds of nucleic acid molecules were released by PEF treatment, a purification of plasmid DNA was impossible at any condition used in this studied. The extraction of nucleic acid molecules by using PEF could be performed within I mini that was shorter period than that of ordinary method.

Ken Hirano, Shunichi Matsuura,
Shinji Katsura, and Akira Mizuno

Department of Ecological Engineering
Toyohashi University of Technology
Tempaku-cho, Toyohashi, Aichi, 441-8113 Japan
Phone: +81-532 44-6904 Fax: +81-532-44-6929
email: mizano@eco.tut.ac.jp

Abstract

An accurate manipulation of a single DNA molecule will support genome analysis, such as mapping and sequencing. This paper describes a novel technique for transportation of a single DNA molecule labeled with a fluorescent dye, and localization of enzymatic activity in a limited area to promote chemical reactions in molecular basis under microscopic observation. The technique uses a focused laser to control temperature of a limited area of about I O llm diameter.

We have developed the following manipulation techniques for single DNA molecule.

(1) Local area melting micromanipulation: In frozen solution, and a small melted area is produced by YAG laser irradiation, and traversed. A DNA molecule is confined in the melted area, and is transported and stretched.

(2) Localization of enzymatic activity: Temperature of the sample is kept at O •C. Restriction enzyme can be activated in a limited area where temperature is increased using the laser irradiation. Yeast chromosomal DNA molecules can be cut by a restriction enzyme (EcoR 1) in the laser focal spot.

Y. N. Gartstein and P. S. Ramesh

Xerox Corporation, Wilson Center for Research and Technology
147-59B, 800 Phillips Rd., Webster, NY 14580

Abstract

Kinetic simulations of a flow of charged particles between two parallel plate electrodes are performed for the case when particles are injected at one of the electrodes with nearly equal initial velocities and are reflectionlessly absorbed by the electrodes upon reaching them. It is shown that such a seemingly simple system can exhibit some fascinating features of nonlinear (dissipative) dynamical systems. A hysteresis between supply limited and space charge limited currents is demonstrated in the current-voltage relation. In agreement with earlier simulations of Birdsall and Bridges, it is found that in the space charge limited regime the system develops self-sustained oscillations, and for a range of voltages multiple stable solutions are possible. Self-supported oscillations of the charged cloud persist even in the absence of the net current through the system. Furthermore, periodically forcing the system can lead to chaotic-like responses in space charge limited currents.

K. Yan, T. Yamamoto, S. Kanazawai, T. Ohkubo,
Y. Nomoto 1 and J. S. Chang2

1 Department of Electrical and Electronic Engineering
Oita University, 700 Dannoharu,
Oita, 87~11, Japan

2 Department of Engineering Physics
McMaster University
Hamilton, Ontario, Canada LOS 4MI

Abstract

In this paper, the effects of CO2 injection rate on the flow stabilized DC corona modes in dry air are experimentally investigated. As an indicator of chemical reactions induced by different corona modes, removal of NO is also studied in gaseous mixtures of N2 + O2 + CO2 + NOx. The transition between glow and streamer can be controlled by on and off of CO2 injection. 95~ of NO can be removed under streamer mode with an energy yield of about 12.5-25 g(NO)/kWh. However, for glow corona mode, the removal of NO is negligible.

T. Sugimoto, S. Doi, and Y. Higashiyama

Yamagata University
Department of Electrical and Information Engineering
4-3-16, Jonan, Yonezawa, 992 8510, Japan
Phone & Fax (+81)238-26-3280
email: toshi @ eie.yz.yamagata-u. ac. jp

Abstract

In order to elucidate a mechanism of the discharge occurring at a grounded electrode located in a space charge cloud, a charged particle cloud was formed and the characteristics of the discharge from the cloud was investigated. Soil conditioning particles charged by negative corona discharge were ejected in a green house forming a space charge cloud with a diameter of around I m and a length of 5 m. Positive streamer corona was observed at the tip of a grounded rod electrode inserted into the negatively charged particle cloud. The magnitude of the discharge current was up to 300 mA depending on the diameter of particles.

J.S.Chang and A.Kwan

Department of Engineering Physics
McMaster University
Hamilton, Ontario, Canada L8S4L7
Telephone: (905) 525-9140, ext. 24924
Fax: (905) 527-5222 email: changj@mcmaster.ca

Abstract

Chemical and physical models of a coaxial wire-pipe negative corona discharge are numerically investigated for dry air. The physical model is based on the one-dimensional model based on experimentally obtained time-averaged discharge current-voltage characteristics as numerical input, where the mobility of electrons is considered as a function of local electric fields. Then the chemical kinetic model is introduced for ions, metastables and radicals for dry air with trace toluene, and calculated based on electron density, electron temperature and electric field profiles obtained from physical model. Negative ions considered in the present model are, Ox- (x = I, 2, 4), NOX(x = 1, 2, 3), N2OX- (x = 2, 4), positive ions considered are Ox+ (x = 1, 2, 4, 6), Nx+(x = 1, 2, 3, 4), NOx+(x = 1, 2, 3, 4), N2OX

(x = 1, 2, 3, 4), and N3+, and radicals are Ox (x = 1, 3), N, NOx (x = I, 2, 3), N2OX (x = I, 4, 5). Numerical results are presented for applied voltages from 13 to 30 kV, gas and flow rate from I to 10 L/min, and toluene concentration from O to 2,000 ppm. The results show that radicals such as O3, N2Os' N2O, NO, O, N, and NO2 are highly concentrated near the corona wire and decrease with increasing distance from corona wire. Negative ions such as are highly concentrated near grounded wall while, has a maximum concentration near the center of the tubes.

Hyun Ha Kim, Graciela Prieto,
Shinji Katsura, Akira Mizuno

Department of Ecological Engineering
Toyohashi University of Technology
Tempaku-cho, Toyohashi 441-8580 Japan
Phone: +81 (532) 444904, Email: mizano@eco.tut.ac.jp

Abstract

In this paper we present a simple equation to explain the removal of NO in a non-thermal plasma reactor. This equation, which relates the change of NO concentration to specific input power (J/L), could provide general insight into the fundamental behavior of pollutant in the plasma reactor. Exponential decrease in the energy constant k was observed with increasing initial concentration and temperature. It has been found that the presence of SO2 in the gas stream greatly enhanced the NO removal.

Mamoru Okumoto, Zhenzhou Su,
Shinji Katsura and Akira Mizuno

Department of Ecological Engineering, Toyohashi University of
Technology
Tempaku-cho, Toyohashi, Aichi, 441~580 Japan
Phone: +81-532 44-6904 Fax: +81-532-44-6929
email: mizano@eco.tut.ac.jp
www: http://mizlab. eco. tut. ac. jp/MizunoLab/MizanoLab. html

Abstract

Direct methanol synthesis from CH4 and O2 has been experimentally studied using pulsed discharge plasma in a concentric-cylinder-type reactor. The methanol production was enhanced by dilution of the source gas with rare gas, such as Ar or He. The methanol production was about 2.5 times larger at the dilution ratio of 2.5 and gradually decreased with increasing the dilution ratio and decreasing the O2 partial pressure. Ethane was formed as one of the by-products, and its concentration became higher as the dilution ratio was increased. The same tendency was observed for Ar and He. On the other hand, when the partial pressure of O2 was kept constant, the methanol production increased up to a saturated level by increasing the dilution, despite the concentration of C2H6 stayed about the same level. Experimental results shown the reaction selectivity for methanol synthesis as dependent on the dilution ratio of the rare gas employed as dilutent.

Istvan Berta, Tibor Horvath, Norbert Szedenik

Technical University of Budapest
Department of High Voltage Engineering and Equipment
]111 Budapest, Egry J. u. 18. HUNGARY

Abstract

Large buildings, governmental offices, groups of buildings depend to an ever increasing extent on electronic equipment and information technology systems. Failures of highly sensitive systems can be caused by lightning strikes. Considering the physical properties of lightning, the detailed data of the building and the electrical and electronic systems inside, complex decision model was created to determine the risk coming into existence with and without different levels of protection. Taking into account the costs of protection and that of the supposed damages, both technically and economically optimized protecting system can be chosen.

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