AE Source Research Articles

The hidden world of Asian tiger mosquitoes: immature Aedes albopictus (Skuse) dominate in rainwater corrugated extension spouts.

The primary sources of Aedes albopictus (Skuse) in its exotic range in North America are artificial containers in backyards, which vary widely in accessibility. In this study we examined their prevalence in two container types that are difficult to inspect: catch basins and corrugated extension spouts (CES), the latter used to divert rainwater in downspouts away from house foundations. We conducted larval and pupal surveys in catch basins, CES and open containers such as buckets and plant saucers in three urban locations in Mercer County, New Jersey, USA. We found that Ae. albopictus were rare in catch basins but prevalent in CES, and were often the only species collected in CES. Specific characteristics of the CES were not significantly associated with the presence or number of Ae. albopictus in them, but those longer and closer to the ground were significantly more likely to contain water, and therefore mosquitoes. During peak season (July-August), the abundance of immature Ae. albopictus was significantly higher in CES than open containers. We found that CES are an important source of Ae. albopictus in our region and propose that effective control strategies should be implemented to minimize mosquito populations from these cryptic habitats.

Acoustic emission source location in plates using wavelet analysis and cross time frequency spectrum

In this study, the theories of wavelet transform and cross-time frequency spectrum (CTFS) are used to locate AE source with frequency-varying wave velocity in plate-type structures. A rectangular array of four sensors is installed on the plate. When an impact is generated by an artificial AE source such as Hsu–Nielsen method of pencil lead breaking (PLB) at any position of the plate, the AE signals will be detected by four sensors at different times. By wavelet packet decomposition, a packet of signals with frequency range of 0.125–0.25MHz is selected. The CTFS is calculated by the short-time Fourier transform of the cross-correlation between considered packets captured by AE sensors. The time delay is calculated when the CTFS reaches the maximum value and the corresponding frequency is extracted per this maximum value. The resulting frequency is used to calculate the group velocity of wave velocity in combination with dispersive curve. The resulted locating error shows the high precision of proposed algorithm.

Acoustic emission study of fatigue crack propagation in extruded AZ31 magnesium alloy

The fatigue crack propagation behavior and corresponding AE characteristics of extruded AZ31 magnesium (Mg) alloy were investigated in this study. The effects of specimen orientation and loading frequency were considered. By combining the AE parameter and waveform analysis with the micro-structural and fractograph observations, the findings of the study showed that crack extension and twinning at the crack tip were two major AE source mechanisms during fatigue crack propagation in the Mg alloy. More twinning events were observed in the transverse direction (TD) specimens than in the extruded direction specimens, which contributed to more cyclic deformation irreversibility and cumulative fatigue damage, leading to worse fatigue performance and higher AE counts in the TD specimens. The results also indicated that increasing the loading frequency could slightly increase the fatigue life, and significantly decrease the AE counts in TD specimens due to the frequency or strain rate dependence of twinning activity. These results suggest that twinning plays an important role in the fatigue process in this Mg alloy, and that the AE technique is capable of detecting crack propagation and twinning events during fatigue.

A Note on Distribution of Breeding Sources of Aedes aegypti (Linnaeus) in the City of Kolkata, India, Following an Outbreak of Dengue during 2012

An Aedes aegypti (larval) survey was conducted by the vector control department of Kolkata Municipal Corporation (KMC), following an outbreak of dengue in Kolkata City in July 2012. Results obtained are startling. Small discarded items were the major breeding sources of Ae. aegypti (prime vector of dengue). Outdoor containers such as battery shells at market places, old tyres at garages and tyre-retreading centres and wells at construction sites represented the first, second and third categories of preferred breeding sites of this vector mosquito. In the past, Ae. aegypti in Kolkata City was quite photophobic with regard to its breeding habit; it used to breed more indoors—mostly in small uncovered masonry tanks used for water storage indoors. But the very mosquito now breeds more outdoors; it has become photophilic. Ecological compulsion created by the people of Kolkata through periodic emptying and cleaning of their masonry tanks and other indoor water storage containers following the KMC’s intensive mass awareness campaigns over the past several years, seemed to have compelled Ae. aegypti to shift its breeding sites from indoors to outdoors for its better survival in the city’s environment. The need for active involvement of some other departments of KMC—besides the health department—such as the departments of solid waste management, building, water supply and drainage, too, was clearly pointed out by the study. Accordingly, multipronged strategies—including prompt destruction of the breeding sources of Ae. aegypti right from the month of January by involving all the concerned departments—were planned and religiously implemented by KMC during 2013. The concerted efforts yielded commendable results: the number of dengue cases downslided from a staggering 1852 (with 2 deaths) in 2012 to a comfortable 238 (with no death) in 2013.

Temporal Patterns of Abundance of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) and Mitochondrial DNA Analysis of Ae. albopictus in the Central African Republic

The invasive Asian tiger mosquito Aedes albopictus (Diptera: Culicidae) was first reported in central Africa in 2000, in Cameroon, with the indigenous mosquito species Ae. aegypti (Diptera: Culicidae). Today, this invasive species is present in almost all countries of the region, including the Central African Republic (CAR), where it was first recorded in 2009. As invasive species of mosquitoes can affect the distribution of native species, resulting in new patterns of vectors and concomitant risk for disease, we undertook a comparative study early and late in the wet season in the capital and the main cities of CAR to document infestation and the ecological preferences of the two species. In addition, we determined the probable geographical origin of invasive populations of Ae. albopictus with two mitochondrial DNA genes, COI and ND5. Analysis revealed that Ae. aegypti was more abundant earlier in the wet season and Ae. albopictus in the late wet season. Used tyres were the most heavily colonized productive larval habitats for both species in both seasons. The invasive species Ae. albopictus predominated over the resident species at all sites in which the two species were sympatric. Mitochondrial DNA analysis revealed broad low genetic diversity, confirming recent introduction of Ae. albopictus in CAR. Phylogeographical analysis based on COI polymorphism indicated that the Ae. albopictus haplotype in the CAR population segregated into two lineages, suggesting multiple sources of Ae. albopictus. These data may have important implications for vector control strategies in central Africa.

10513 家兎膝蓋腱の擬似生体環境下における損傷挙動のAE法による評価(OS2-4【バイオエンジニアリング(4)】)

AE monitoring of damage process of rabbit patellar tendon under static tensile load was carried out. Considering strong viscoelasticity of tendon, load was applied at various loading rate (10, 1, 0.1 mm/min) until the complete rupture in physiological saline at 37°C. The displacement of the specimen was monitored by a digital video camera, and acquired images were used for determining the displacement distribution in tendon by the digital image correlation (DIC) technique. It was found that the average failure stress increased as loading rate increased, and the differences in maximum stress were considered to be statistically significant. AE signals were detected before the maximum load and AE source locations corresponded to the locally elongated area, which indicates that fascicle failure takes place before the maximum load. Consequently, the fundamental insights for the damage monitoring technique which are indispensable for the optimization of programs of sports training or rehabilitation are obtained.

Experimental Consideration about AE Sources Location of a Thin CFRP Vessel Pressure Test

Experimental Consideration about AE Sources Location of a Thin CFRP Vessel Pressure Test

Three-dimensional analytical solution of acoustic emission or microseismic source location under cube monitoring network

To find the analytical solution of the acoustic emission/microseismic(AE/MS) source location coordinates, the sensor location coordinates were optimized and simplified. A cube monitoring network of sensor location was selected, and the AE/MS source localization equations were established. A location method with P-wave velocity by analytical solutions (P-VAS) was obtained with these equations. The virtual location tests show that the relocation results of analytical method are fully consistent with the actual coordinates for events both inside and outside the monitoring network; whereas the location error of traditional time difference method is between 0.01 and 0.03 m for events inside the sensor array, and the location errors are larger, which is up to 1080986 m for events outside the sensor array. The broken pencil location tests were carried out in the cross section of 100 mm×98 mm, 350 mm-length granite rock specimen using five AE sensors. Five AE sources were relocated with the conventional method and the P-VAS method. For the four events outside monitoring network, the positioning accuracy by P-VAS method is higher than that by the traditional method, and the location accuracy of the larger one can be increased by 17.61 mm. The results of both virtual and broken pencil location tests show that the proposed analytical solution is effective to improve the positioning accuracy. It can locate the coordinates of AE/MS source only using simple four arithmetic operations, without determining the fitting initial value and iterative calculation, which can be solved by a conventional calculator or Microsoft Excel.

Acoustic emission monitoring of hydraulic fracturing laboratory experiment with supercritical and liquid CO2

Carbon dioxide (CO2) is often used for enhanced oil recovery in depleted petroleum reservoirs, and its behavior in rock is also of interest in CO2 capture and storage projects. CO2usually becomes supercritical (SC‐CO2) at depths greater than 1,000 m, while it is liquid (L‐CO2) at low temperatures. The viscosity of L‐CO2is one order lower than that of normal liquid water, and that of SC‐CO2is much lower still. To clarify fracture behavior induced with injection of the low viscosity fluids, we conducted hydraulic fracturing experiments using 17 cm cubic granite blocks. The AE sources with the SC‐ and L‐CO2injections tend to distribute in a larger area than those with water injection, and furthermore, SC‐CO2tended to generate cracks extending more three dimensionally rather than along a flat plane than L‐CO2. It was also found that the breakdown pressures for SC‐ and L‐CO2 injections are expected to be considerably lower than for water.

A Study on Localization of Acoustic Emission Source Based on Algebraic Neural Network

We propose the concept of algebraic neural network and introduce the algebraic algorithm in the network-training phase, which transforms the complex nonlinear optimization problem to a set of simple algebraic equations and achieves the best result directly. The experimental results show that rub-impact AE source localization problem is well solved by combining the nonlinear dynamic features and neural network, thus to provide cue to rotor rub-impact fault diagnosis and the application prospects and further research values are promising.

J022024 種々のひずみ速度下における家兎膝蓋腱の損傷過程のAE法による評価

AE monitoring of damage process of rabbit patellar tendon under static tensile load was carried out. Considering strong viscoelasticity of tendon, load was applied at various loading rate (10, 1, 0.1 mm/min) until the complete rupture in physiological saline at 37℃. The displacement of the specimen was monitored by a digital video camera, and acquired images were used for determining the displacement distribution in tendon by the digital image correlation (DIC) technique. It was found that AE signals were detected before the maximum load and AE source locations corresponded to the locally elongated area, which indicates that fascicle failure takes place before the maximum load. The average failure stress increased as loading rate increased, and the differences in average failure stress were considered to be statistically significant. Consequently, the fundamental insights for the damage monitoring technique which are indispensable for the optimization of programs of sports training or rehabilitation are obtained.

Acoustic Emission Study of Corrosion Fatigue and Fatigue for API 5L X70 Gas Pipeline Steel

Acoustic emission is a very important test among non-destructive tests, and it has been applied for the detection of failures in various types of equipment in the petroleum industry, such as pressure vessels, tanks and pipelines. In this study, the effect of pre-existing uniform corrosion on the corrosion fatigue specimen and smooth specimen on fatigue behaviour of API 5L X70 steel pipeline in long life range was investigated by using acoustic emission in fatigue test. The presence of pre-existing uniform corrosion specimen, produces by 4 month immersion in sulphuric acid, H2SO4 (concentration 0.2 ml H2SO4 in 5000 ml deionized water ). Fully reverse (R = -1) constant amplitude fatigue test were done in corrosion fatigue and smooth specimen in different stress amplitudes. It was found that, effect of pre-existing uniform corrosion significantly reduced the fatigue life of the steel pipeline. The correlations of accumulative AE counts for corrosion fatigue higher than fatigue test because of the mechanisms of possible AE sources due to corrosion.

The use of acoustic emission for bearing condition monitoring

This paper reports research currently in progress at Swansea University in collaboration with SKF Engineering & Research Centre as part of a continuing investigation into high frequency Acoustic Emission. The primary concerns are experimentally producing subsurface cracks, the type of which would occur in a service failure of a ball bearing, within a steel ball and to closely monitor the properties of this AE from crack initiation to the formation of a ball on the ball surface. It is worth noting that there is evidence that the frequency content of the AE changes during this period, although this has yet to be proved consistent or even fully explained. Conclusive evidence could lead to a system which detects such cracks in a bearing operating in real life conditions, advantageous for many reasons including safety, downtime and maintenance and associated costs.The results from two experimental procedures are presented, one of which loads a single ball held stationary in a test rig to induce subsurface cracks, which are in turn detected by a pair of broadband AE sensors and recorded via a Labview based software system. This approach not only allows detailed analysis of the AE waveforms but also approximate AE source location from the time difference between two sensors.The second experimental procedure details an adaptation of a four-ball lubricant tester in an attempt to produce naturally occurring subsurface cracks from rolling contact whilst minimising the AE arising from surface wear. This thought behind this experiment is reinforced with 3D computational modelling of the rotating system.

The Study of Identification Method for the Welding Defect Source of Low-Alloy High-Strength Steel Based on AE Technology

Three-bending test has been performed on the standard specimen and welding specimen with defect of low-alloy and high-strength steel in order to simulate the failure process of structural parts under loading, and the AE activities (number of hits) and stress-strain curve were measured during the whole loading process. The law of acoustic emission signals at different deformation stages has been investigated and the relation between AE characteristic parameters and the different deformation stages has been established. The typical AE waveforms such as friction noise, plastic deformation, welding microcrack initiation and propagation are obtained, which are analyzed by using spectrum characteristics analytical method. The spectrum characteristic parameters such as average frequency, peak frequency and frequency centroid, energy percentage of frequency spectrum part I and III of the typical AE defect signals are extracted, the distributing range of which are initially set. Study shows these five parameters have a closely relation with the nature of the AE signals, and based on these characteristics parameters different AE sources can be preliminary identified correctly. The study can provide some guidance to the practical application of AE acoustic emission technology in the industrial field.

Development of chromosome 6D-specific markers for α-gliadin genes and their use in assessing dynamic changes at the Gli-2 loci

To develop chromosome 6D-specific point mutation (PM) markers for α-gliadin genes, 79 α-gliadin sequences cloned from Aegilops tauschii and another 40 α-gliadin genes with known chromosome locations were used in multi-sequence alignment and phylogenic analysis. Additional multiple alignment adjustments were performed manually to facilitate discovery of putative chromosome 6D-specific point mutations. A total of 85 PM primers were designed to detect 68 candidate chromosome 6D-specific point mutations. Experimental tests revealed 11 chromosome 6D-specific PM markers by using genomic DNA from homoeologous group 6 nullisomic–tetrasomic lines of Chinese Spring and putative diploid and tetraploid ancestors of hexaploid wheat as PCR templates. Detection of PM markers in one synthetic hexaploid wheat and its parental lines indicated that some α-gliadin genes were lost from Gli-2 loci during the formation of hexaploid wheat by amphidiploidization of the genomes of Triticum turgidum and Ae. tauschii. Detection of these PM markers in Ae. tauschii, T. aestivum and its four subspecies indicated that at least two genetically distinct sources of Ae. tauschii contributed germplasm to the D genome of T. aestivum.

OS11-3-3 Estimation of AE Source Mechanisms in Bonding Surface between Base Concrete and Repairing Material under Shear Tests

OS11-3-3 Estimation of AE Source Mechanisms in Bonding Surface between Base Concrete and Repairing Material under Shear Tests

AE Monitoring of Damage Accumulation in Transparent Conductive Oxide Film under the Mechanical Strain

In this study, tensile tests of the transparent conductive oxide (TCO) deposited on the polyethylene naphthalate (PEN) films (TCO + PEN films) used in dye-sensitized solar cells (DSCs) were carried out. In order to discriminate the AE signals in TCO from PEN films, PEN film specimens (TCO was removed by 17.5% hydrochloric acid) were also prepared. It was found from the tensile tests that many AE signals were detected in TCO + PEN films, while AE activity in PEN films was much lower. On the other hand, the electric resistance of TCO was also measured during tensile tests. The remarkable increase in AE event rate was recognized at the strain of ∼0.63%, while the electric resistance increased rapidly at the strain of 0.68%. These results demonstrated that the critical damage in TCO was detected by the measurement of AE signals more sensitively than the electric resistance measurement. To identify AE sources, in-situ observation of specimen during tensile test with AE measurement was carried out. During tensile test, cracks transverse to the loading direction in the TCO were found at the strain of 0.67%, and then saturated at the strain of ∼9%. Cracks parallel to the loading direction in TCO were initiated at the strain of 9.63%. On the other hand, the remarkable increase in AE event rate was recognized at the strain of ∼0.7%. It reached a peak at the strain of ∼2%, and then decreased, and increased again at the strain of ∼10%. It was then concluded that AE behavior corresponds to the cracking behavior in TCO. Consequently, it was suggested that AE technique could be a powerful technique for evaluating the damage accumulation process in DSCs.

OS11F089 Estimation of AE Source Mechanisms in Bonding Surface between Existing Concrete and Repairing Material under Shear Tests

OS11F089 Estimation of AE Source Mechanisms in Bonding Surface between Existing Concrete and Repairing Material under Shear Tests

Herschelobservations of the hydroxyl radical (OH) in young stellar objects

<i>Aims. <i/>“Water In Star-forming regions with <i>Herschel<i/>” (WISH) is a <i>Herschel<i/> key program investigating the water chemistry in young stellar objects (YSOs) during protostellar evolution. Hydroxyl (OH) is one of the reactants in the chemical network most closely linked to the formation and destruction of H<sub>2<sub/>O. High-temperature (<i>T<i/> 250 K) chemistry connects OH and H<sub>2<sub/>O through the OH + H<sub>2<sub/> H<sub>2<sub/>O + H reactions. Formation of H<sub>2<sub/>O from OH is efficient in the high-temperature regime found in shocks and the innermost part of protostellar envelopes. Moreover, in the presence of UV photons, OH can be produced from the photo-dissociation of H<sub>2<sub/>O through H<sub>2<sub/>O + <i>γ<i/><sub>UV<sub/> OH + H.<i>Methods. <i/>High-resolution spectroscopy of the 163.12 <i>μ<i/>m triplet of OH towards HH 46 and NGC 1333 IRAS 2A was carried out with the Heterodyne Instrument for the Far Infrared (HIFI) on board the <i>Herschel<i/> Space Observatory. The low- and intermediate-mass protostars HH 46, TMR 1, IRAS 15398-3359, DK Cha, NGC 7129 FIRS 2, and NGC 1333 IRAS 2A were observed with the Photodetector Array Camera and Spectrometer (PACS) on <i>Herschel<i/> in four transitions of OH and two [O i] lines.<i>Results. <i/>The OH transitions at 79, 84, 119, and 163 <i>μ<i/>m and [O i] emission at 63 and 145<i>μ<i/>m were detected with PACS towards the class I low-mass YSOs as well as the intermediate-mass and class I Herbig Ae sources. No OH emission was detected from the class 0 YSO NGC 1333 IRAS 2A, though the 119 <i>μ<i/>m was detected in absorption. With HIFI, the 163.12 <i>μ<i/>m was not detected from HH 46 and only tentatively detected from NGC 1333 IRAS 2A. The combination of the PACS and HIFI results for HH 46 constrains the line width (<i>FWHM<i/> 11 km s<sup>-1<sup/>) and indicates that the OH emission likely originates from shocked gas. This scenario is supported by trends of the OH flux increasing with the [O i] flux and the bolometric luminosity, as found in our sample. Similar OH line ratios for most sources suggest that OH has comparable excitation temperatures despite the different physical properties of the sources.

THE DISK IMAGING SURVEY OF CHEMISTRY WITH SMA. I. TAURUS PROTOPLANETARY DISK DATA

Chemistry plays an important role in the structure and evolution of protoplanetary disks, with implications for the composition of comets and planets. This is the first of a series of papers based on data from DISCS, a Submillimeter Array survey of the chemical composition of protoplanetary disks. The six Taurus sources in the program (DM Tau, AA Tau, LkCa 15, GM Aur, CQ Tau and MWC 480) range in stellar spectral type from M1 to A4 and offer an opportunity to test the effects of stellar luminosity on the disk chemistry. The disks were observed in 10 different lines at ~3" resolution and an rms of ~100 mJy beam-1 at ~0.5 km s-1. The four brightest lines are CO 2-1, HCO+ 3-2, CN 2_3-1_2 and HCN 3-2 and these are detected toward all sources (except for HCN toward CQ Tau). The weaker lines of CN 2_2-1_1, DCO+ 3-2, N2H+ 3-2, H2CO 3_03-2_02 and 4_14-3_13 are detected toward two to three disks each, and DCN 3-2 only toward LkCa 15. CH3OH 4_21-3_12 and c-C3H2 are not detected. There is no obvious difference between the T Tauri and Herbig Ae sources with regard to CN and HCN intensities. In contrast, DCO+, DCN, N2H+ and H2CO are detected only toward the T Tauri stars, suggesting that the disks around Herbig Ae stars lack cold regions for long enough timescales to allow for efficient deuterium chemistry, CO freeze-out, and grain chemistry.