Journal of AE, Volume 25, 2007 (ca. 26 MB) - AEWG

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A relation between AE activity and half-cell potentials in the accelerated corrosion test is given in Fig. 13. Two periods of high AE activity (hits) are observed. At the first period, the half-cell potentials start to decrease, where an abrupt increase in AE hits is observed at around three days. The potentials reach lower than –350 mV (C.S. E) after the second period. Because such two periods as the onset of corrosion in reinforcement and the nucleation of cracking in concrete due to the expansion of corrosion products are defined in the standards, the two high AE activities are quite suggestive in the deterioration process due to the corrosion of reinforced concrete. To classify AE sources (micro-cracks) in the corrosion process, AE parameter analysis was performed. Variations of RA values and the average frequencies in the cyclic wet-dry test are given in Fig. 14. Two stages are reasonably identified from the figure. During the first period of around 40 days elapsed, RA value is high and the average frequency is low. From Fig. 6, this suggests that shear cracks are actively generated. It is considered that shear cracks occur in reinforcement due to the onset of corrosion or rust breakage. During the second period around 100 days elapsed, RA value in Fig. 14 is lower than the first period and the average frequency is high. This implies the occurrence of tensile cracks. The expansion due to corrosion products should result in the nucleation of tensile cracks in concrete. Consequently, it is reasonable to consider that the second high AE activity corresponds to the nucleation of concrete cracking. Fig. 14 Variations of AE parameters. Chloride concentrations at the cover-thickness were also investigated to compare with AE results. It was found that chloride concentrations at reinforcement were higher than 0.3 kg/m 3 after the first period and became higher than 1.2 kg/m 3 after the second. These results are in good agreement with the values prescribed as the lower bound and the upper bound for the corrosion in the specification. (4) Mechanisms of Corrosion Cracking A concrete specimen of dimensions 25 cm x 25 cm x 10 cm with a hole of 3-cm diameter was tested. The hole corresponds to rebar location with 4-cm cover-thickness. The compressive strength of concrete at 28-day standard curing was 37.9 MPa. The velocity of P wave was 4730 m/s and the modulus of elasticity was 29.7 GPa. P-wave velocity was applied to SiGMA 30
analysis. Corrosion cracking was simulated by casting an expansive agent (dolomite paste) into the hole. After one day, three cracks were macroscopically observed as shown in Fig. 15. These are surface crack and two diagonal cracks. Results of SiGMA analysis are plotted at locations of AE sources with crack types and orientations in the same figure. At the meso-scale, all the types of micro-cracks are observed as AE sources in SiGMA analysis. This implies that micro-cracks are accumulated and macroscopically the cracks are nucleated as the surface crack and the diagonal cracks. In the photo, the crack, which propagated from the hole to the bottom, corresponds to the surface crack. Around this crack, numerous tensile cracks of AE sources are observed, which are almost oriented as vertical to the surface-crack plane. During the test, the surface crack was observed first, and then two diagonal cracks propagated. Around these cracks, AE sources are composed of tensile, mixed-mode and shear cracks. It is noted that the final cracks of the surface crack and the diagonal cracks consist of one crack surface at the macro-scale, but actually many micro-cracks are nucleated around them. This is a typical cracking mechanism in concrete. Mechanisms of corrosion cracking in concrete are of crack-opening failure, but the cracks follow zigzag paths, thus explaining nearly equal contributions of mixed-mode and shear cracks at the meso-scale. 4. Conclusion Fig. 15 Observed cracks (left) and visualized results of SiGMA analysis (right). (1) The recommended practice (NDIS 2421) is applied to cyclic bending tests of reinforced concrete beams. The applicability of the criterion to qualifying the damage is confirmed. Thus, it is demonstrated that the criterion to assess the damage is useful for inspection of beams in service. (2) Applying AE rate process analysis to compression tests of concrete cores, it is demonstrated that relative damages estimated are in reasonable agreement with actual damages. The procedure is promising to estimate the damage of concrete quantitatively without knowing initial properties at construction. (3) It is found that AE monitoring could provide earlier warning of the corrosion than the half-cell potentials. By continuously monitoring AE activity, both the onset of corrosion in reinforcement and the nucleation of cracking in concrete could be identified nondestructively. 31
Page 3 and 4: JOURNAL OF ACOUSTIC EMISSION VOLUME
Page 5 and 6: 25-194 ACOUSTIC EMISSION SOURCE LOC
Page 7 and 8: Volume 25 (2007) AUTHORS INDEX DIMI
Page 9 and 10: YUICHI TOMODA, 25-021 T. TOUTOUNTZA
Page 11 and 12: Notes for Contributors 1. General T
Page 13 and 14: In Memoriam H. Reginald Hardy, Jr.
Page 15 and 16: STRUCTURAL INTEGRITY EVALUATION USI
Page 17 and 18: The power-law AE behavior was recen
Page 19 and 20: sorting out the original signals, e
Page 21 and 22: Wood [36] in Australia has been usi
Page 23 and 24: One needs to appreciate the difficu
Page 25 and 26: In geotechnical applications, the p
Page 27 and 28: methods include the use of combined
Page 29 and 30: should take. Past attempts for stru
Page 31 and 32: 11. Suzuki, T., Ohtsu, M., Aoki, M.
Page 33 and 34: 40. http://en.wikipedia.org/wiki/Ma
Page 35 and 36: Abstract ACOUSTIC EMISSION TECHNIQU
Page 37 and 38: Fig. 1 Damage qualification by the
Page 39 and 40: After adding the data of a tested s
Page 41 and 42: Fig. 8 Sketch of a reinforced concr
Page 43: (3) Corrosion Process of Reinforced
Page 47 and 48: ACOUSTIC EMISSION MONITORING OF REI
Page 49 and 50: which - contrary to current beliefs
Page 51 and 52: Fig. 4. Applied load (actuator 1) a
Page 53 and 54: concrete and the jacket. Visual ins
Page 55 and 56: Based on conventional analysis, AE
Page 57 and 58: 2. Experimental The model pipe syst
Page 59 and 60: pressure, respectively. This is ana
Page 61 and 62: Fig. 6: Power spectra from fast Fou
Page 63 and 64: small leaks (below 0.1 mm diameter)
Page 65 and 66: ACOUSTIC EMISSION TECHNIQUE APPLIED
Page 67 and 68: parameters in time domain and (c) m
Page 69 and 70: above the threshold level of 40 dB
Page 71 and 72: energy, i.e., high amplitude and lo
Page 73 and 74: An optical microscopy observation o
Page 75 and 76: Continuous WT (CWT) is defined as a
Page 77 and 78: Fig. 8. Typical AE waveforms, their
Page 79 and 80: followed by abrupt jumps in the det
Page 81 and 82: E. Landis (1999), “Micro-macro fr
Page 83 and 84: EVALUATION OF REPAIR EFFECT FOR DET
Page 85 and 86: Fig. 2 Sensor array for tomography
Page 87 and 88: 2 [ ] 2 k 3 9 2 2 1 f () 0 f ()
Page 89 and 90: At these depths, a complicated and
Page 91 and 92: The number of AE hits after repair
Page 93 and 94: damage indices of Calm and Load rat
Page 95 and 96:
PVDF is a semicrystalline polymer,
Page 97 and 98:
After these preliminary tests, the
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of PVDF sensors does not seem to ha
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Fig. 10. Evolution of a typical PAD
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Fig. 17. Evolution of a typical dur
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I-G. Kim, H-Y. Lee and J-W. Kim (20
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Pencil-lead breaks are monopoles an
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Fig. 1 Displacement vs. time, sourc
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Fig. 5 Displacement vs. time, sourc
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Fig. 8 Displacement versus time for
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Fig. 10 Displacement vs. time. Sour
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Fig. 14 Signal amplitude versus tim
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To better relate these PLB and FEM
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HIGH-TEMPERATURE ACOUSTIC EMISSION
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thickness of 9 μm. The AlN element
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Fig. 5 Experimental setup for AE mo
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scales (and possibly salt cracks at
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DAMPING, NOISE, AND IN-PLANE RESPON
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The sharper resonance in Fig. 1c is
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i 2 RMS VDCC0 k BT = , g m 2 i
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ecause in-plane motion mostly produ
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4. B. Bahreyni, C. Shafai, Fabricat
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We first introduce our new quadridi
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Fig. 4 Amplitude profile as a funct
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Fig. 6 Change of room temperature (
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3) There are slight time lags in th
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Function Generator (FG) The functio
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Table 1 Results for continuous sens
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Fig. 7 pulse response XXX, filter :
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Fig. 11: Noise spectrum VS30-SIC-46
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waves propagate in a plate like str
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0.15 0 100kHz Driving pulse 10 100k
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0.45 0 100kHz Driving pulse 30 100k
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the sensor response to different fr
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CHARACTERISTICS OFACOUSTIC EMISSION
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Results and Discussion Shrinkage pr
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sapwood. Norway spruce wood consist
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most of the cells reached the fiber
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CHARACTERIZATION OF TITANIUM HYDRID
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Growth behavior of hydrides We stud
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were determined by the tensile test
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Figure 9 shows the Mode-I cracks in
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Results obtained are summarized as
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process of hydrogen destruction of
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Amplitude [dB] 60 55 50 45 40 35 30
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(Fig. 7) relative to the material a
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is shown in Table 1. Test specimens
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Fig. 4 Two types of AE signals dete
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the charging solution at 25 o C, by
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ANALYSIS OF ACOUSTIC EMISSION FROM
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nearly same waveforms for the first
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values). Most (11 of 14) of the rec
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Type-D (at 3.45 ms). In this sample
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NEURAL NETWORK BURST PRESSURE PREDI
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temperature, while the remaining se
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not properly set). This results in
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Conclusions Table 3 Summary of trai
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accurate source locations could be
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Fig. 1 Group velocities versus freq
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plane source orientation. But the l
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Fig. 9 Out-of-plane displacement vs
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Fig. 11 WTs of Fig. 8 with superimp
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Fig. 13 WTs of Fig. 10 with superim
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Table 3 At 102 kHz, WT peak arrival
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Fig. 17 Frequency of maximum WT int
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Fig. 18 Arrangement of sensors (#1,
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location calculation result that yi
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NOVEL ACOUSTIC EMISSION SOURCE LOCA
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tion resolution. It should be noted
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The specimen with numerous holes wa
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Fig. 5. Comparison of location meth
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Conclusions Delta-T source location
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Our approach This conceptual view c
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Voronoi Construction: Taking a case
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Fig. 6: Source location on a clamp
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PROBABILITY OF DETECTION FOR ACOUST
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POD is determined at the convergenc
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Fig. 2: Setup for illustrative runs
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Fig. 7: Probability of location (PO
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AE signals were filtered by high-pa
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Fig. 3 Accuracy and variations of a
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Fig. 7 Accuracy and variations of a
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eference data. The absolute values
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REAL-TIME DENOISING OF AE SIGNALS B
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600 500 400 300 200 kHz700 Frequenc
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the STFT result (Fig. 4(b)). Theref
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MONITORING THE EVOLUTION OF INDIVID
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the type of filtering, number of su
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was observed for either actuator. F
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Conclusions An experimental methodo
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the onset of pulses, consequently,
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zeros. The locations where a patter
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The reliability of the additional p
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AE MONITORING OF SOIL CORROSION OF
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Fig. 2 Cumulative AE counts with ap
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cumulative event counts and amplitu
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AE was monitored using three types
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Our conclusion from these tests is
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measurements with an Exxon Nuclear
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equipment manufacturer), CISE (AE t
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Automatic testing of receptacles du
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The finalized standards are: • EN
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14. Tscheliesnig P., Lackner G., He
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Fig. 1. Typical high-temperature cr
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• Emission rates are much higher
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Fig. 4. Results of AE monitoring of
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examination at 2000-5000X was able
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samples extracted from the beam aft
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The relative comparison of the size
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Fig. 3. Schema of VB Application fo
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Fig. 5. Microstructural observation
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Fig. 7 AE source locations for diff
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Fig. 9 CT images and corresponding
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A.M. Brandt, G. Prokopski, J. Mater
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conducted with AE technique. The AE
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After location of the events, inter
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The transit times of the individual
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6) B. Schechinger, T. Vogel, Acoust
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greater than the available anchorag
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location uncertainty and is the roo
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Figures 4 and 5 illustrate all loca
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ig cracks form, localization of AE
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ased on magnetic induction, while i
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Fig. 3. AE sensors positioning on b
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As a further evaluation of the degr
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EARLY FAULT DETECTION AT GEAR UNITS
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Acoustic Emission Analysis at Rotat
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The fixed bearing at the beginning
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The time-frequency components of a
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Additionally, the gear test bench h
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APPLICATION OF ACOUSTIC EMISSION IN
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Measurements of the acoustic backgr
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Fig. 6. RMS for different ranges of
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which indicate the transition from
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surface condition. It has already b
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( 2 1) 2) ! kx1 ! k c ! x + c ! k (
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Fig. 6: Signal above normal and def
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DAMAGE ASSESSMENT OF GEARBOX OPERAT
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The waveform streaming can be trigg
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Extracting features using different
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The classifier was used to identify
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ASL spectral energy is further calc
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2 #_ of _ Sensors 2 2 2 ( x ) (
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Simulated Failure Plane One hundred
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It has been documented that the ini
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(a) (b) (c) (d) 95% _ 98% 98% _ 100
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IMPACT IMAGING METHOD TO MAP DAMAGE
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e) Step d) was repeated until the a
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Panel A Panel B Panel C Panel D Fig
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Journal of AE, Volume 25, 2007 (ca. 26 MB) - AEWG

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