Excitation Method for Thermosonic Non-destructive Testing

Thermosonics is a non-destructive testing method in which cracks in an object are made visible through the local generation of heat caused by friction and/or stress concentration. The heat is generated through the dissipation of mechanical energy at the crack interfaces by vibration. The temperature rise around the area close to the crack is measured by a high-sensitivity infrared imaging camera whose field of view covers a large area. The method therefore covers a large area from a single excitation position so it can provide a rapid and convenient inspection technique for structures with complex geometry and small and closed cracks. An ultrasonic horn, originally designed for welding, has generally been used for thermosonic testing. However, it is diffcult to obtain reproducible and controllable excitation with the existing horn system because of non-linearity in the coupling; surface damage can also be produced by chattering caused by loss of contact between the tip of the horn and the structure. Therefore, the general aim of the study was to develop a reliable and convenient excitation method that should excite sufficient vibration for the detection of the defects of interest at all relevant positions in the structure and must also avoid surface damage. In this thesis, a numerical and experimental study for the development of the ex- citation method for reliable thermosonic testing is presented. Successful excitation methods for the detection of delaminations in composites and cracks in metal struc- tures are described. A simple, small wax-coupled PZT exciter is introduced as a con- venient, reliable thermosonic test system in applications where relatively low strain levels are required for damage detection such as composite plates. A reproducible vibration exciter may be su cient for thermosonic testing in some metal structures such as a thin plates. However, higher strain levels are often required in metal structures, though the required strain level is dependent on the crack size. This level of strain is not easily achieved within the reproducible vibration range because of non-linearity in the contact between the exciter and the structure. Therefore, studies are conducted with an acoustic horn with high power capability to investi- gate the characteristics of the vibration produced in a real structure with complex geometry and to develop a excitation method for achieving reliable excitation in the non-linear vibration range for thermosonic testing. An excitation method for a complicated metallic structure such as a turbine blade is also investigated and the in uence of the clamping method and the excitation signal that is input to the horn on the vibration characteristics generated in the testpiece is presented. As a result, a fast narrow band sweep test with a general purpose amplifier and stud coupling is proposed as an excitation method for thermosonic testing. This method can be ap- plied to different types of turbine blades and also to other components. One typical characteristic of a thermosonic test using non-linear vibration is the lack of repeata- bility in the amplitude and the frequency characteristic of the vibration. Therefore, vibration monitoring is necessary for reliable thermosonic testing and a Heating In- dex(HI) has been proposed as a criterion indicating whether su cient vibration is achieved in a tested structure or not. The HI is calculated from different vibration records measured by different sensors and these results are compared in this thesis. A microphone can provide a cheaper and more convenient non-contacting vibration monitoring device than a laser or strain gauge and the heating index calculated by a microphone signal shows similar characteristics to that calculated from the other sensors

Picture Quality and Sound Quality of OLED TVs

Unlike the past when cathode-ray tube (CRT) dominated display industry, many different types of flat panel displays (FPDs) are now leading the industry. Of these, organic light-emitting diode (OLED) display has recently become a next-generation display since this display is recognised as having advantages over other competing technologies in picture quality and form factor. With major attributes of picture quality considered, a series of evaluations based on objective measures was performed with an OLED TV compared to an LCD TV. OLED TV outperformed LCD TV 100 times in black, 20 times in colour contrast, 30% in dynamic range coverage, 50 times in local contrast and 20 times in viewing angle. In addition, sound quality of the OLED TV was assessed using both objective and subjective evaluation methods compared to conventional TV speakers since OLED panel speaker technology was recently commercialised. The OLED panel speaker showed better performance both in objective and subjective methods

A longer look at the asymmetric dependence between hedge funds and the equity market

Author name used in this publication: Byoung Uk Kang2009-2010 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

A novel method for the preparation of non-agglomerated nanometre sized particles of lanthanum phosphate phosphors utilising a high surface area support in the firing process

This journal is © The Royal Society of Chemistry 2012A convenient method is described that uses a quartz wool substrate to immobilise nanometre sized phosphor precursor particles enabling them to be fired at high temperature without sintering/agglomeration. The nanometre sized phosphor particles are easily removed from the substrate by re-dispersion into liquid for subsequent use.Biotechnology and biological sciences research council (BBSRC

Structural studies on Helicobacter pylori ATP-dependent protease, FtsH

The crystal structures of the Helicobacter pylori FtsH ATPase domain in the nucleotide-free state and complexed with ADP have been determined

Giant Cell Tumor of Soft Tissue: a Case with Atypical US and MRI Findings

We report the case of a giant cell tumor with diffuse interstitial hemorrhaging and unusually prominent cystic components in the soft tissue of the thigh which has not been reported previously. Magnetic resonance image (MRI), showed signal intensity typical of a giant cell tumor. However, because of its conspicuous large well-circumscribed cystic components, the differential diagnoses, based on the image findings from an ultrasonography (US) and MRI, were complicated epidermoid cyst, cystic change of a neurogenic tumor, and a parasitic cyst

Behavioral and transcriptomic analysis of Trem2-null mice: Not all knockout mice are created equal

It is clear that innate immune system status is altered in numerous neurodegenerative diseases. Human genetic studies have demonstrated that triggering receptor expressed in myeloid cells 2 (TREM2) coding variants have a strong association with Alzheimer\u27s disease (AD) and other neurodegenerative diseases. To more thoroughly understand the impact of TREM2 in vivo, we studied the behavioral and cognitive functions of wild-type (WT) and Trem2-/- (KO) mice during basal conditions and brain function in the context of innate immune stimulation with peripherally administered lipopolysaccharide (LPS). Early markers of neuroinflammation preceded Aif1 and Trem2 upregulation that occurred at later stages (24-48 h post-LPS). We performed a transcriptomic study of these cohorts and found numerous transcripts and pathways that were altered in Trem2-/- mice both at baseline and 48 h after LPS challenge. Importantly, our transcriptome analysis revealed that our Trem2-/- mouse line (Velocigene allele) results in exaggerated Treml1 upregulation. In contrast, aberrantly high Treml1 expression was absent in the Trem2 knockout line generated by the Colonna lab and the Jackson Labs CRISPR/Cas9 Trem2 knockout line. Notably, removal of the floxed neomycin selection cassette ameliorated aberrant Treml1 expression, validating the artifactual nature of Treml1 expression in the original Trem2-/- Velocigene line. Clearly further studies are needed to decipher whether the Treml1 transcriptional artifact is functionally meaningful, but our data indicate that caution is warranted when interpreting functional studies with this particular line. Additionally, our results indicate that other Velocigene alleles or targeting strategies with strong heterologous promoters need to carefully consider downstream genes

The Effects of the Acupuncture Treatment for Smoking Cessation in High School Student Smokers

The use of alternative medicine for smoking cessation have been increasing steadily in recent years. A series of clinical group studies was performed to clarify the effect, outcome and success rate of an acupuncture treatment for smoking cessation. This study was conducted for four weeks using 238 smoking students at 2 high schools. The subjects were separated into two groups: 159 students were treated with acupuncture on the anti-smoking acupoints of the ear, which is known to be effective for cessation of smoking (case group), and 79 students were treated at other sites of the ear (control group). The acupuncture treatment was alternately administered at each side of the ears on a weekly basis for 4 weeks. The smoking cessation success was only 1 case (0.6%) in the case group and none in the control group after 4 weeks. The change in the taste of tobacco and the intensity of the desire to smoke were not significantly different between the case and control groups, but the case group showed a tendency of reduction in the taste of tobacco and the intensity of the desire to smoke. In addition, the reduction in cigarette consumption was not significant, but the tendency of reduction in the study group was significant. It is believed that the site of auricular acupuncture for smoking cessation is not important. However, there was a significant tendency in terms of the reduction in cigarette consumption, the taste of tobacco and the intensity of the desire to smoke in the case group, indicating that auricular acupuncture in smoking cessation has some effect

Crystal structure of Helicobacter pylori MinE, a cell division topological specificity factor

In Gram-negative bacteria, proper placement of the FtsZ ring, mediated by nucleoid occlusion and the activities of the dynamic oscillating Min proteins MinC, MinD and MinE, is required for correct positioning of the cell division septum. MinE is a topological specificity factor that counters the activity of MinCD division inhibitor at the mid-cell division site. Its structure consists of an anti-MinCD domain and a topology specificity domain (TSD). Previous NMR analysis of truncated Escherichia coli MinE showed that the TSD domain contains a long α-helix and two anti-parallel β-strands, which mediate formation of a homodimeric α/β structure. Here we report the crystal structure of full-length Helicobacter pylori MinE and redefine its TSD based on that structure. The N-terminal region of the TSD (residues 19–26), previously defined as part of the anti-MinCD domain, forms a β-strand (βA) and participates in TSD folding. In addition, H. pylori MinE forms a dimer through the interaction of anti-parallel βA-strands. Moreover, we observed serial dimer–dimer interactions within the crystal packing, resulting in the formation of a multimeric structure. We therefore redefine the functional domain of MinE and propose that a multimeric filamentous structure is formed through anti-parallel β-strand interactions