Structural Health Monitoring of Cracked Aircraft Panels Repaired with Bonded Patches Using Fiber Bragg Grating Sensors

Structural health monitoring of cracked aircraft panels repaired with bonded patches for extending the service life of aging aircraft has received wide attention. In this paper, the identification of the locations and shapes of fatigue crack and disbond fronts in aircraft panels repaired with double-sided bonded patches using fiber Bragg grating (FBG) sensors is studied. The identification is performed by minimizing the difference between the detected and calculated reflection spectra of FBG sensors at multiple positions on the free surface of patches. The validity and effectiveness of the identification in practical use is verified by comparing the identification results with the exact ones.     

Microbial communities and their interactions in biofilm systems: an overview.

Several important advances have been made in the study of biofilm microbial populations relating to their spatial structure (or architecture), their community structure, and their dependence on physicochemical parameters. With the knowledge that hydrodynamic forces influence biofilm architecture came the realization that metabolic processes may be enhanced if certain spatial structures can be forced. An example is the extent of plasmid-mediated horizontal gene transfer in biofilms. Recent in situ work in defined model systems has shown that the biofilm architecture plays a role for genetic transfer by bacterial conjugation in determining how far the donor cells can penetrate the biofilm. Open channels and pores allow for more efficient donor transport and hence more frequent cell collisions leading to rapid spread of the genes by horizontal gene transfer. Such insight into the physical environment of biofilms can be utilized for bioenhancement of catabolic processes by introduction of mobile genetic elements into an existing microbial community. If the donor organisms themselves persist, bioaugmentation can lead to successful establishment of newly introduced species and may be a more successful strategy than biostimulation (the addition of nutrients or specific carbon sources to stimulate the authochthonous population) as shown for an enrichment culture of nitrifying bacteria added to rotating disk biofilm reactors using fluorescent in situ hybridization (FISH) and microelectrode measurements of NH4+, NO2-, NO3-, and O2. However, few studies have been carried out on full-scale systems. Bioaugmentation and bioenhancement are most successful if a constant selective pressure can be maintained favoring the promulgation of the added enrichment culture. Overall, knowledge gain about microbial community interactions in biofilms continues to be driven by the availability of methods for the rapid analysis of microbial communities and their activities. Molecular tools can be grouped into those suitable for ex situ and in situ community analysis. Non-spatial community analysis, in the sense of assessing changes in microbial populations as a function of time or environmental conditions, relies on general fingerprinting methods, like DGGE and T-RFLP, performed on nucleic acids extracted from biofilm. These approaches have been most useful when combined with gene amplification, cloning and sequencing to assemble a phylogenetic inventory of microbial species. It is expected that the use of oligonucleotide microarrays will greatly facilitate the analysis of microbial communities and their activities in biofilms. Structure-activity relationships can be explored using incorporation of 13C-labeled substrates into microbial DNA and RNA to identify metabolically active community members. Finally, based on the DNA sequences in a biofilm, FISH probes can be designed to verify the abundance and spatial location of microbial community members. This in turn allows for in situ structure/function analysis when FISH is combined with microsensors, microautoradiography, and confocal laser scanning microscopy with advanced image analysis.     

Role of cyclooxygenase-2 in the healing of gastric ulcers in rats

Extracellular activity was recorded from single spinal dorsal horn neurons in both chronic cat and acute rat models. This was done to define the effects of anesthesia on the processing of sensory information elicited by nonnoxious tactile stimulation of peripheral receptive fields (RFs). In the chronic cat model, baseline data were obtained in physiologically intact, awake, drug-free animals before anesthetic administration (halothane 1.0-2.0%). This made it possible to compare and contrast activity of each cell in the drug-free and anesthetized state. Halothane effects were confirmed in the acute rat model (anesthetized, spinally transected, and in some cases decerebrate). In addition, the gamma-aminobutyic acid-A (GABAA)-receptor antagonist picrotoxin (2 mg/kg) was administered intravenously to verify that the observed halothane effect on spinal dorsal horn neurons was mediated by an interaction with GABAA-receptor systems. Halothane effects on three separate measures of response to nonnoxious tactile stimuli were observed in the chronic cat model. Halothane produced a significant, dose-dependent reduction in the low-threshold RF area of the neurons studied. Halothane also caused a significant reduction in neuronal response to RF brushing (dynamic stimulus) and to maintained contact with the RF (static stimulus). A dose dependency was not observed with these latter two effects. Neurons with a predominant rapidly adapting response seemed to be less susceptible to halothane suppression than slowly adapting cells. In the acute rat model an increase in halothane caused a reduction in neuronal response similar to that seen in the cat. The intravenous administration of 2 mg/kg of picrotoxin by itself caused no significant change in RF size or response to brushing. However, the same amount of picrotoxin did cause a 50% reversal of the halothane-induced reduction in RF size without causing a significant change in the halothane effect on response to RF brushing. In contrast to work recently reported in a chronic sheep model, halothane causes a significant reduction in spinal dorsal horn neuronal response to tactile stimulation of peripheral RFs. This effect is caused by, in part, but not exclusively, to GABAA-neurotransmitter systems. However, the relative influence of GABAA systems may vary with the nature of the stimulus.     

Insulation characteristics of GIS under nonstandard lightning impulse oscillations: Insulation characteristics under double‐frequency oscillations with various frequencies and damping ratios

To improve GIS insulation specifications, it is important to recognize the insulation characteristics under oscillatory overvoltage waveforms occurring in the field. This paper describes investigations of insulation characteristics for double‐frequency oscillatory waveforms with various frequencies and damping ratios. It was found that minimum breakdown voltages (V_min) were irrelevant to frequency changes in the range of experimental conditions under the same damping conditions. On the other hand, V_min rose with the damping ratio rising under the same frequency conditions. The insulation characteristics at a valley of oscillation were investigated using actual breakdown voltages. It was found that the insulation characteristics were treated all‐inclusively based on the characteristics of V_min for damping time. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(2): 11–19, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10245     

Motion and size estimation of a free moving metallic particle in GIS based on propagation properties of acoustic waves

We have investigated the propagation properties of Lamb waves and motion characteristic of free moving metallic particle in a gas‐insulated switchgear (GIS) tank to diagnose the insulation performance of GIS. We have proposed a new identification technique for defect location in GIS based on the time–frequency analysis of the Lamb waves using the Wavelet Transform. In this paper, we measured the acoustic signals excited by a metallic particle colliding with the tank sheath. Furthermore, we measured the moving particles under a high electric field in GIS using a high‐speed video camera. As a result, we examined the relationship between maximum lifting height and the flight time during subsequent impacts of a moving particle. Moreover, we estimated particle size based on the propagation properties of Lamb waves. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(1): 26–33, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20023     

Creep crack growth characteristics of polypropylene film at various temperatures

Creep crack growth rates were measured using centrally cracked tension specimens of thin polypropylene film at various temperatures and stress levels. The creep crack growth rates were correlated with the stress intensity factor. The experimental results showed that there is the region of the minimum constant crack growth rate which occupies more than 75% of the total creep failure life. This steady or constant creep crack growth rate depends on the test temperature and the initial stress intensity factor. The constant creep crack growth rate characteristics were analyzed on the basis of the Arrhenius type thermally activated process. It is found that creep crack growth behavior is closely related to the crack tip opening displacement and the creep zone size.     

The cytoprotective effect of leminoprazole on indomethacin-induced damage to rabbit gastric mucosal cells

Leminoprazole (an acid pump inhibitor) has a mucosal protective effect against various experimental gastric lesions, but the underlying mechanism remains unknown. We examined whether leminoprazole prevents indomethacin-induced damage to cultured gastric mucosal cells. The viability of rabbit gastric mucosal cells was assessed by the 3-(4,5-dimethyl-2-thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide and dye exclusion methods. [35S]Methionine-labeled proteins were detected by autoradiography after sodium dodecylsulfate-polyacrylamide gel electrophoresis. Western blot analysis was carried out using anti-heat shock protein (HSP)-70 and anti-HSP-72 antibodies. Exposure of gastric mucosal cells to indomethacin for 4 hr apparently reduced their viability in a dose-related manner. Pretreatment with leminoprazole for 4 hr significantly prevented the reduction in cell viability caused by 50 microM indomethacin, although omeprazole was not effective. However, such pretreatment did not prevent the severe damage induced by 500 microM indomethacin. 16,16-Dimethyl prostaglandin E2 significantly prevented the cell damage induced by indomethacin at both 50 and 500 microM. Leminoprazole alone did not affect cell viability. The cytoprotection by leminoprazole was expressed after a 2-hr lag period. Leminoprazole did not promote prostaglandin E2 synthesis by cells, but it apparently induced the synthesis of 83-kDa, 72-kDa, 52-kDa and 35-kDa proteins. Both the cytoprotection and the induction of such protein synthesis were abolished by cycloheximide and actinomycin D. The leminoprazole-induced 72-kDa protein did not react with the antibodies against HSP-70 and HSP-72. These results indicate that leminoprazole directly protects gastric mucosal cells against mild damage caused by indomethacin and that its cytoprotective effect might be mediated through de novo synthesized proteins. In addition, it is suggested that the leminoprazole-induced proteins might be unknown proteins related to cytoprotection, although the exact characters of the proteins are unclear.     

Proposal for new particle deactivation methods in GIS

This paper deals with consideration of particle motion control and its trapping in the deactivation of foreign contaminating moving particle in simulated GIS. The particle motion behavior in nonuniform field gap without/with different shaped spacers was investigated experimentally under DC and 60 Hz AC voltages. The obtained results were confirmed experimentally as well as by calculating the electrostatic force acting on the particle in the nonuniform field gap and are reported elsewhere. Whereas, in this paper, the observed particle motion behavior around simple shaped spacer is simulated by solving the particle motion equations analytically in the presence of electrical gradient and image forces. The simulation agreed fairly well with the experimental results. Furthermore, in the nonuniform electric field, the effect of dielectric coating on the grounded electrode on the particle motion and particle deactivation is also briefly discussed. On the basis of the obtained results of particle motion behavior without/with different shaped spacers and the effect of dielectric coating on the ground electrode, different methods of particle deactivation are suggested as well as confirmed experimentally     

Evaluation of breakdown characteristics of gas insulated switchgears for non-standard lightning impulse waveforms - analysis and generation circuit of non-standard lightning impulse waveforms in actual field

To lower the insulation specifications (specifically, the lightning impulse withstand voltage) of a gas insulated switchgear (GIS) and thus cut the equipment cost while maintaining the high reliability of its insulation performance, it is necessary to define in an organized way the insulation characteristics for non-standard lightning impulse voltage waveforms that represent actual surge waveforms in the field and compare them with the characteristics for the standard lightning impulse waveform quantitatively. In this paper, first, lightning surge waveforms and disconnector switching surge waveforms at UHV, 500 kV, and 275 kV substations were analyzed and five non-standard lightning surge waveforms with basic frequencies of 0.6 to 5.0 MHz were identified. Next, high-voltage circuits that generate these non-standard lightning surge waveforms were designed and constituted using EMTP (electro magnetic transients program) based on a circuit with a gap, inductors, and resistors connected in series and resistors and capacitors connected in parallel. Further, circuits were actually constructed, to obtain voltage waveforms approximately equal to those designed. Finally, the dielectric breakdown voltage-time characteristics were measured under several different conditions for the quasi-uniform SF₆ gas gap that represents an insulation element of a GIS. As a result, it was found that, in the tested range, the dielectric breakdown values for non-standard lightning impulse waveforms were higher than for the standard lightning impulse waveform by 6% to 32%