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EP1272837A2 - Detection non destructive de la degradation d'elements renforcateurs - Google Patents

Detection non destructive de la degradation d'elements renforcateurs

Info

Publication number
EP1272837A2
EP1272837A2 EP01924896A EP01924896A EP1272837A2 EP 1272837 A2 EP1272837 A2 EP 1272837A2 EP 01924896 A EP01924896 A EP 01924896A EP 01924896 A EP01924896 A EP 01924896A EP 1272837 A2 EP1272837 A2 EP 1272837A2
Authority
EP
European Patent Office
Prior art keywords
bar
measurement
determining
degradation
inducing
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP01924896A
Other languages
German (de)
English (en)
Inventor
David W. Blodgett
George L. Vojtech
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Johns Hopkins University
Original Assignee
Johns Hopkins University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Johns Hopkins University filed Critical Johns Hopkins University
Publication of EP1272837A2 publication Critical patent/EP1272837A2/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/12—Analysing solids by measuring frequency or resonance of acoustic waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/11—Analysing solids by measuring attenuation of acoustic waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/024—Mixtures
    • G01N2291/02458—Solids in solids, e.g. granules
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/04—Wave modes and trajectories
    • G01N2291/042—Wave modes
    • G01N2291/0427—Flexural waves, plate waves, e.g. Lamb waves, tuning fork, cantilever

Definitions

  • This invention relates to a method of and apparatus for detecting the degradation of a reinforcing member. More specifically, this invention relates to nondestructive detection of degradation of a reinforcing member embedded within a structure.
  • Concrete is an artificial stone made from a mixture of water, aggregate (such as sand and gravel), and a binder (such as cement). Because of its potential for immense strength, its initial ability to adapt to virtually any form, and its resistance to fire, concrete has become one of the most common building materials in the world.
  • reinforcing members like stone, concrete is strong in compression and weak in tension. Thus concrete is commonly strengthened by embedding reinforcing members ("re-bar”) within it. Concrete containing embedded strengthening members is known as "reinforced concrete.” Reinforcement allows less concrete to be used because the reinforcing member provides tensile strength.
  • Re-bar may take many forms, but is commonly in the form of steel reinforcing bars. Re-bar contributes tensile strength to concrete. Plain concrete does not easily withstand stresses such as wind action, earthquakes, vibrations, and other bending forces, and is therefore unsuitable in many structural applications. With reinforced concrete, the tensile strength of re-bar and the compressional strength of concrete render a member capable of sustaining many types of heavy stresses over considerable spans. In normal reinforced concrete structures, cracking must occur to allow for the transfer of tensile stresses from the concrete to the steel. These cracks allow for the penetration of chlorides through the concrete. The penetration of chlorides has been directly linked with re-bar degradation.
  • the present invention provides a system that is easily realizable with current technology and insensitive to external variables. If suspect concrete is found, then a more advanced imaging technique, such as GPR, IE, UPV, or conventional plug, could be employed to confirm the problem and determine the extent of the structural degradation of the concrete.
  • a more advanced imaging technique such as GPR, IE, UPV, or conventional plug, could be employed to confirm the problem and determine the extent of the structural degradation of the concrete.
  • resonance is used to detect structural member degradation.
  • Sound is produced by the vibrations of a body and is transmitted through material media in pressure waves made up of alternate condensations (forcing of the molecules of the medium together) and rarefactions
  • Degradation can arise from many sources, such as corrosion, fracture, cracking, fatigue, chemical reaction, etc.
  • the present invention provides a nondestructive method for early detection of a degraded reinforcing member in a structure.
  • the present invention allows detection of degradation of re-bar in structures, such as concrete structures, by using resonance.
  • This method termed "modal analysis,” uses, for example, an audio speaker to generate vibrational resonant modes in buried re-bar in reinforced concrete structures.
  • the buried re-bar then acts as an acoustic source, generating acoustic waves.
  • the generated waves propagate to the surface of the concrete, where they are detected and analyzed.
  • the present invention can generate acoustic waves in the re-bar without physically contacting the structure or the re-bar. This is beneficial since it may not always be possible to generate re-bar vibrations by contact in field conditions and since physical contact may damage the structure or re-bar being tested.
  • Another technique for generating vibrational resonant modes in buried re-bar is using a laser to generate acoustic waves in a concrete structure. Absorption of a short pulse laser by a material results in localized thermal expansion and subsequent generation of broadband acoustic waves. This technique allows for complete non- contact generation of the required acoustic waves that would be beneficial for characterizing hard-to-reach sections of a concrete structure.
  • the concrete bonds to the re-bar.
  • the concrete structure has a different harmonic frequency than does the re-bar.
  • the concrete is not excited by the same frequency of waves that excite the re-bar.
  • the concrete is bonded to the re-bar, the concrete provides resistance to the vibration of the re-bar. That is, the concrete acts to damp the vibrating re-bar.
  • the re-bar effectively disbonds or separates from the surrounding concrete.
  • a greater vibration corresponds to a lesser degree of bonding, which corresponds to a greater degree of re-bar degradation.
  • Measurements were performed on several specially prepared concrete blocks with re-bar of varying degrees of simulated degradation. Results from these measurements indicated that the damping constant of the resonant mode increases with increasing level of disbond. Field measurements on an old bridge over the Patuxent River at the Howard County/Montgomery County border in Maryland confirmed these results and showed that the center frequency of the resonant mode can also be used as an indication of re-bar degradation.
  • resonant modes above about 4 kHz were specifically linked to the presence of re-bar degradation.
  • Figure 1 is a graphical representation of an example resonant frequency measurement of a vibrating re-bar embedded within concrete
  • Figure 2 is a graphical comparison of example resonant frequency measurements from both bonded and unbonded re-bar;
  • Figure 3 is a schematic representation of a preferred embodiment of the present invention
  • Figure 4 is an enlarged view of the portion of Figure 3 enclosed by the dashed box;
  • Figure 5 is a graphical comparison of the measured frequency spectra for a first set of laboratory experiments
  • Figure 6 is an enlarged view of one of the peaks of Figure 5;
  • Figure 7 is a graphical comparison of the measured frequency spectra for a second set of laboratory experiments;
  • Figure 8 is a graphical comparison of the measured frequency spectra for a third set of laboratory experiments.
  • Figure 9 is an enlarged view of one of the peaks in Figure 8;
  • Figure 10 is a measurement of a first field test;
  • Figure 11 is a measurement of a second field test
  • Figure 12 is a measurement of a third field test.
  • the purpose of the present invention is to develop a portable, non-imaging, non-destructive evaluation technique and device capable of detecting a degraded reinforcing member.
  • the preferred embodiment of the present invention takes advantage of the acoustic resonance properties of re-bar in concrete in order to determine if significant re-bar degradation is present.
  • the physical dimensions and elastic properties determine the resonant frequencies of the re-bar.
  • the damping constant, Q depends on the bonding of the re-bar to the concrete. Undegraded re-bar is expected to be well bonded to the concrete. However, as the re-bar degrades and expands, it effectively disbonds from the surrounding concrete, resulting in an increase of the damping constant Q.
  • the bonding characteristics (and thereby the presence of degradation) can be determined.
  • the two important components for a portable system are the efficient generation of resonant frequencies in the re-bar and the subsequent monitoring of its resonant frequency vibrations .
  • the present invention takes advantage of the modal properties of the re-bar in the concrete structure to determine if significant re-bar degradation has occurred.
  • the fundamental resonant mode of a cylindrical rod (although reinforcing members may take various forms, a cylindrical rod will be discussed for illustrative purposes only) is given by: where E is the elastic modulus, r is the radius of the rod, L is the length of the rod, and p is the density. Equation 1 shows that the fundamental frequency is very sensitive to the radius and length of the re-bar. However, although not shown in this equation, the resonant frequency also depends on the medium surrounding the rod. Specifically, the resonant frequency of the rod is found to decrease as the viscosity of the medium surrounding the medium increases.
  • any change in the resonant frequency could be attributed to a change in the viscosity of the surrounding medium.
  • FIG. 1 is a graphical representation of an example resonant frequency measurement of a vibrating re-bar embedded within concrete. The horizontal axis is a measure of frequency and the vertical axis is a measure of amplitude.
  • a simulated measurement 10 of a re-bar vibration is shown. In Figure 1, it is seen that measurement 10 is centered on a resonant frequency f R .
  • the amount of damping - and therefore the amount of re-bar to concrete bonding and the amount of re-bar degradation - can be determined by calculating the damping constant Q of the measured response.
  • the damping constant Q of the re-bar is calculated by determining the ratio of the center frequency to the width of the resonant peak at 0.707 the peak (maximum) amplitude. That is, where R is the measured resonant frequency of the re-bar and fi and f 2 are the frequencies corresponding to an amplitude of 0.707 that of the peak amplitude.
  • Figure 2 is a simulated graphical comparison of resonant frequency measurements from both bonded and unbonded re-bar. Similarly to Figure 1, the horizontal axis is a measure of frequency and the vertical axis is a measure of amplitude. Measurement 20 is a typical response from unbonded re-bar, while measurement 30 is a typical response from bonded re-bar.
  • unbonded measurement 20 has a greater resonant frequency and narrower resonant peak than does bonded measurement 30. This is due to the damping effect of the concrete on the bonded re-bar. Since there is less damping associated with unbonded re-bar than with bonded re-bar, the damping constant for unbonded re-bar is greater than the damping constant for bonded re-bar. That is,
  • re-bar degradation can also be determined by looking at the center frequencies of the detected resonant modes. Due to the size and mass of typical concrete structures, one would not expect to detect resonant modes above a few kilohertz. Any resonant modes above this threshold frequency could be attributed to disbonded (degraded) re-bar.
  • FIG. 3 is a schematic representation of a preferred embodiment of a measuring device 200.
  • a structure 100 containing re-bar 110 is shown in the form of a piling. It should be understood that the method and device of the present invention may be used on a structure of any form.
  • Measuring device 200 is positioned proximate structure 100 in order to determine the presence of re-bar 110 degradation.
  • Device 200 comprises a vibration inducing instrument 210 and a measuring instrument 220.
  • Vibration inducing instrument 210 may take various forms, such as a speaker or a laser.
  • Inducing instrument 210 is used to generate acoustic waves within structure 100.
  • Inducing instrument 210 should be positioned adjacent structure 100, and preferably is coupled directly to structure 100 by, for example, clamping.
  • Measuring instrument 220 is used to detect the induced vibrations of the structure 100 and re-bar 110.
  • Measuring instrument 220 is preferably positioned adjacent structure 100.
  • Measuring instrument 220 detects the character (frequency, amplitude, etc.) of the vibrations induced by inducing instrument 210. The measurements can then be analyzed to determine the presence of re-bar degradation.
  • measuring instrument 220 is a laser vibrometer.
  • a laser vibrometer is compact and easy to use, and can measure the vibration frequency and amplitude of any surface from a relatively large distance away from the surface.
  • an accelerometer - or any other surface vibration sensing tool - may be used as measuring instrument 220.
  • Measuring instrument 220 may include a display for displaying the measurements to allow the user to analyze the measurements to determine the presence of re-bar degradation. A separate display may also be provided.
  • FIG 4 is an enlarged view of the portion of Figure 3 enclosed by the dashed box 400.
  • Inducing instrument 210 emits vibration inducing waves 410. Waves 410 propagate through structure 100 and impact re-bar 110, inducing re-bar 110 to vibrate. The vibrating re-bar 110 produces acoustic waves 420. Waves 420 propagate through structure 100.
  • Measuring instrument 220 detects waves 420 at a surface 102 of structure 100. These measurements are then analyzed to detect the presence of re-bar 110 degradation.
  • Metallic tape maybe coupled to surface 102 to enhance readability of the vibrations by measuring device 220. Other enhancers, such as a small piece of aluminum sheet coupled to the concrete structure, may also be used. Enhancers are not necessary if measuring instrument 220 is of sufficient strength.
  • Device 200 may also comprise a controller 230.
  • controller 230 is a computer. Use of controller 230 is beneficial because it can help ensure the desired frequencies are generated accurately by using a feedback loop in known fashion to control the energy imparted to the structure. Controller 230 can also help ensure efficient generation of the resonant modes in the re-bar by ramping the output of inducing instrument 210 over a range of outputs while simultaneously measuring the responses via measuring instrument 220. Additionally, controller 230 allows multiple readings to be taken at each frequency.
  • An amplifier 240 may be used to increase the energy in the waves 410 imparted to structure 100 and the waves 420 detected by measuring instrument 220.
  • controller 230 employs a software program that allows the user flexibility in the control of device 200. It is desirable that the user be able to specify the start and stop parameters, specify the number of samples obtained at each measurement step, specify the acquisition time, specify the measurement step interval, record the magnitude and phase of the measured signal, and save the results in a file for later processing.
  • a preferred commercially available software program is Lab VIEWTM, which is commercially available from National InstrumentsTM.
  • FIG. 13 is a flowchart of a preferred analysis process 1300.
  • process 1300 is automated by a software program.
  • Process 1300 begins at step 1310 by prompting the user to input the desired parameters for the measurement. Such parameters may include, among others, the start and stop limits, the number of samples obtained at each step, the acquisition time, and the step interval.
  • the parameters are received from the user at step 1320.
  • a measurement process is calculated at step 1330.
  • the calculated measurement is then performed and data collected at step 1340. This acquired data is then stored at step 1350. Storing the data allows the user to perform subsequent analysis of the data.
  • the data is analyzed at step 1360.
  • Process 1300 preferably includes calculating the percentage of re-bar degradation at step 1370. These results are then displayed to the user at step 1380. In a preferred embodiment, the percentage of re- bar degradation is displayed at step 1380.
  • the highest resolution frequency spectra are obviously obtained by making the frequency step of the waves 410 imparted by inducing instrument 210 as small as possible.
  • the signal to noise ratio ("SNR") of the measurement can also be improved by averaging multiple readings at each step.
  • SNR signal to noise ratio
  • inducing instrument 210 was a speaker and a frequency step size of 1 Hz was used with 10 samples per frequency step.
  • a first set of laboratory experiments was conducted on a concrete block containing a perfectly bonded, half bonded, and completely unbonded piece of re-bar.
  • the partially (half) disbonded re-bar had foam wrapped along the full backside of the re-bar (as opposed to only the right- or left-hand side of the re-bar).
  • Access ports were placed in the block to provide visual inspection of the buried re-bar. These access ports allowed direct comparison of the measured re-bar resonant modes with what was detected at the surface of the concrete.
  • a speaker was used as inducing instrument 210.
  • Speaker 210 was placed on top of the concrete block as the resonant spectrum for each re-bar was measured.
  • Figure 5 is a graphical comparison of the measured frequency spectra for the first set of laboratory experiments. Two prominent peaks 510, 520 are seen. Peak 510 is at about 1400 Hz and peak 520 is at about 1900 Hz. Peak 520 is believed due to a flexural mode of the concrete itself, while peak 510 is due to the re-bar.
  • Figure 6 is an enlarged view of peak 510 of Figure 5. Measurements from all three re-bar are seen. Measurement 610 is a measurement of the completely bonded re- bar, measurement 620 is a measurement of the partially bonded re-bar, and measurement 630 is a measurement of the completely unbonded re-bar. As expected, the damping constant Q of the re-bar increases with the degree of disbond.
  • FIG. 7 is a graphical comparison of the measured frequency spectra for the second set of laboratory experiments.
  • Measurement 710 is a measurement of the unbonded re-bar made from the re-bar itself
  • measurement 720 is a measurement of the unbonded re-bar made from the surface of the concrete structure.
  • the resonant peaks at about 1900 Hz are substantially identical, which would be expected if they are actually due to a flexural mode of the concrete block itself.
  • the peaks at about 1400 Hz are of more importance, particularly the second resonant peak in measurement 720.
  • Measurement 720 was measured from the front surface of the concrete. The decrease in the amplitude of the peak is attributed to attenuation of the acoustic energy as the acoustic waves propagate from the re-bar through the structure to the surface of the concrete.
  • FIG. 8 is a graphical comparison of the measured frequency spectra for the third set of laboratory experiments. Two distinct sets of resonant peaks 810, 820 are seen. Peak 810 is near 2.8 kHz, and peak 820 is near 3.2 kHz.
  • Figure 9 is an enlarged view of peak 810, which is due to unbonded re-bar.
  • Measurement 910 is a measurement of the completely bonded re-bar
  • measurement 920 is a measurement of the partially bonded re-bar
  • measurement 930 is a measurement of the completely unbonded re-bar.
  • the unbonded measurement 930 has a damping constant Q of about 66. It is difficult to estimate the damping constants Q for the partially bonded and fully bonded re-bar. However, the damping constants Q for the unbonded and partially bonded re-bar resonant mode near 3.2 kHz are more easily measured. These are about 49 and 44, respectively.
  • damping constants Q show the expected trend per the level of disbond, but may not have the level of sensitivity required for predicting the actual degree of disbond. Further measurements were made for the unbonded re-bar from the re-bar itself and from the concrete surface. As before, the spectra were very similar except for the expected loss of signal due to acoustic wave attenuation.
  • the amplitude of the resonant mode is smaller along the longitudinal axis of the re-bar than it is perpendicular to the re-bar. This is believed to be due to the radiative field from the acoustic source (re-bar). Knowledge of the expected radiative field can therefore be used to determine the orientation of the disbonded re-bar.
  • Figure 10 is a measurement of the first picket (containing surface cracks). The presence of high frequency readings on the right-hand side of the spectrum indicates the presence of re-bar degradation.
  • Figure 11 is a measurement of the second picket (no surface cracks). The absence of high frequency readings indicates the absence of re-bar degradation.
  • any physical structure in the field will produce resonant frequencies drastically different from those of Figures 10 and 11. That is, the resonant frequency response from physical structures in the field will not vary significantly from those of Figures 10 and 11. Thus, it is safe to assume that any measured resonant frequencies exceeding about 4 kHz are due to the presence of re-bar. It may optionally be desired to analyze these high frequency readings to determine the amplitude of the measurements as an additional step in the analysis. It may optionally be desired to analyze these high frequency readings to determine the damping constant Q as an additional step in the analysis.
  • the pickets were subsequently removed from the bridge and destructively inspected for signs of re-bar degradation. Visual inspection confirmed the experimental results.
  • the re-bar in the first picket showed heavy signs of degradation, while the re- bar in the second picket appeared to be in good shape.
  • Figure 12 is a measurement of this third field test. As with the good picket of Figure 11, there is minimal high-frequency content in the measured spectrum. The small peak near 8 kHz may be due to either re-bar or a drainage pipe that ran inside the bridge base that emptied out just below and to the right of our measurements. The low damping constant Q of this resonant mode suggests that whatever was generating this resonant mode was well bonded to the surrounding concrete.

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
  • Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)

Abstract

L'invention concerne un procédé et un dispositif, non destructifs, de détection de la dégradation d'éléments renforçateurs encastrés dans une structure, cette dégradation pouvant être provoquée par plusieurs facteurs tels que la corrosion, des cassures, fractures, l'usure, les réactions chimiques, etc.. Ce dispositif comprend un instrument inducteur, destiné à induire la vibration des éléments renforçateurs, ainsi qu'un instrument de mesure, destiné à détecter la vibration desdits éléments. La mesure est alors analysée aux fins de détection d'une dégradation des éléments renforçateurs ou de la présence d'une liaison entre ces éléments et le béton. Le dispositif de l'invention peut comporter un module de commande, aux fins d'amélioration de la détection, et il peut encore comporter un amplificateur destiné à accroître davantage l'énergie des ondes communiquées à la structure et celle des ondes acoustiques détectées par l'instrument de mesure.
EP01924896A 2000-04-13 2001-04-11 Detection non destructive de la degradation d'elements renforcateurs Withdrawn EP1272837A2 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US19707900P 2000-04-13 2000-04-13
US197079P 2000-04-13
PCT/US2001/011637 WO2001079831A2 (fr) 2000-04-13 2001-04-11 Detection non destructive de la degradation d'elements renforcateurs

Publications (1)

Publication Number Publication Date
EP1272837A2 true EP1272837A2 (fr) 2003-01-08

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EP (1) EP1272837A2 (fr)
AU (1) AU2001251505A1 (fr)
CA (1) CA2404102A1 (fr)
WO (1) WO2001079831A2 (fr)

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RU2327136C1 (ru) * 2006-12-11 2008-06-20 ООО "Научно-производственное предприятие "Метакон" Способ контроля наличия отслоений арматуры в железобетонных изделиях
WO2012125837A1 (fr) 2011-03-15 2012-09-20 Purdue Research Foundation Détection de liaison faible
CN108844856B (zh) * 2018-07-04 2023-08-15 四川升拓检测技术股份有限公司 基于冲击弹性波和机器学习的套筒灌浆缺陷无损检测方法

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US5144838A (en) * 1989-10-04 1992-09-08 Iwatsu Electric Co., Ltd. Defect detecting method and apparatus
FR2666656A1 (fr) * 1990-09-11 1992-03-13 Thomson Csf Procede et dispositif d'inspection d'une structure par analyse modale.
DE4239221A1 (de) * 1992-11-21 1994-05-26 Otto Dr Rer Nat Kroggel Ultraschallreflexions-Verfahren zur Trennrißerkennung in Stahlbeton
US5652386A (en) * 1993-03-03 1997-07-29 Washington University Method and apparatus for predicting sturctural integrity by estimating modal damping factor
US5505090A (en) * 1993-11-24 1996-04-09 Holographics Inc. Method and apparatus for non-destructive inspection of composite materials and semi-monocoque structures
US5520052A (en) * 1994-02-10 1996-05-28 The United States Of America As Represented By The United States Department Of Energy Method and apparatus for determining material structural integrity
US5540096A (en) * 1994-06-07 1996-07-30 Washington Suburban Sanitary Commission Method for the non-destructive evaluation of prestressed concrete structures
CA2169307C (fr) * 1994-12-12 2003-10-14 David A. Hutchins Inspection et caracterisation sans contact de materiaux faisant appel a des transducteurs ultrasoniques

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Title
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Also Published As

Publication number Publication date
CA2404102A1 (fr) 2001-10-25
WO2001079831A2 (fr) 2001-10-25
AU2001251505A1 (en) 2001-10-30
WO2001079831A3 (fr) 2002-08-15

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