Rayleigh Wave Calibration of Acoustic Emission Sensors and Ultrasonic Transducers.

Acoustic emission (AE) sensors and ultrasonic transducers were characterized for the detection of Rayleigh waves (RW). Small aperture reference sensors were characterized first using the fracture of glass capillary tubes in combination with a theoretical displacement calculation, which utilized finite element method (FEM) and was verified by laser interferometer. For the calibration of 18 commercial sensors and two piezoceramic disks, a 90° angle beam transducer was used to generate RW pulses on an aluminum transfer block. By a substitution method, RW receiving sensitivity of a sensor under test was determined over the range of frequency from 22 kHz to 2 MHz. Results were compared to the sensitivities to normally incident waves (NW) and to other guided waves (GW). It was found that (1) NW sensitivities are always higher than RW sensitivities, (2) differences between NW and RW receiving sensitivities are dependent on frequency and sensor size, (3) most sensors show comparable RW and GW receiving sensitivities, especially those of commonly used AE sensors, and (4) the receiving sensitivities of small aperture (1 mm diameter) sensors behave differently from larger sensors

Structural Health Monitoring of Large Structures Using Acoustic Emission-Case Histories

Acoustic emission (AE) techniques have successfully been used for assuring the structural integrity of large rocket motorcases since 1963 [...

タバコ懸濁培養細胞におけるアルミニウムの二価鉄、銅およびカドミウム毒性に対する影響

The effects of aluminum (Al) on the cytotoxicity of ferrous iron (Fe(Ⅱ)), copper(Cu) and cadmium(Cd) were studied. Log-phase cells were treated with either FeSO4,CuSO4, or CdCl2 in the presence or absence of AlCl3(120μM) for 18h at pH 4.0. After the treatment, the viability was determined as relative growth of the metal-treated cells to the untreated control cells during the post-treated culture. A single treated with either Al, Fe(Ⅱ) or Cd did not inhibit the growth at the metal concerntrations up to 300 μM, 200 μM and 500 μM, respectively, whereas the growth was markedly inhibited at 15 μM Cu. Thus,the cells were relatively insensitive to Al, Fe(Ⅱ) and Cd and sensitive to Cu. When cells were treated with both Fe(Ⅱ)(120 μM)and Al(120μM), the growth was significantly inhibited and the cellular contents of both Al and Fe increased synergistically. After the treatment with Cu(0 to 10 μM) with or without Al, the cells grew more vigorously when they were treated in the presence of Al, althrouh the Cu content of the cells were not alterd by Al. The presence of Al during the treatmemt with Cd(0 to 2 μM) had no effect on the degree of growth inhibition by Cd. Thus, Al interacts with the toxicity of Fe(Ⅱ), Cu and Cd in different manners; synergistic with Fe(Ⅱ), antagonistic with Cu and apparently no effeco on Cd.二価鉄[Fe(Ⅱ)]、銅（Cu)およびカドミウム（Cd）の細胞毒性に対するアルミニウム（Al）の効果について検討した。120μM AlCl3の存在もしくは非存在下において、対数増殖期の細胞をFeSO4,CuSO4,CdCl2で各々18時間、pH4.0で処理した。処理後の生存率は、処理後の細胞を増殖させたのちに、未処理細胞（コントロール）の増殖に対する金属で処理した細胞の相対増殖率で求めた。Al,Fe(Ⅱ),Cdの単独処理による増殖阻害は、各々300μM、200μM、500μMの濃度まで観察されなかったが、Cuでは15μMで大きく阻害された。このように、タバコ細胞は相対的にAl、Fe（Ⅱ）、Cdには感受性が低く、Cuには感受性が高かった。細胞をFe（Ⅱ）およびAlの両方で処理すると、増殖は著しく阻害され、AlおよびFeの細胞内含量も相乗的に増加した。Cuで処理した場合、Alを加えることにより逆に増殖率が増加した。しかし、細胞内Cu含量はAlの影響を受けなかった。Cd処理の場合、Alを加えてもCdによる増殖阻害の程度は変わらなかった。このように、AlはFe（Ⅱ）、Cu、Cd毒性に対して各々異なる相互作用を示し、Fe（Ⅱ）に対し、相乗効果を、Cuに対しては拮抗的な阻害を示したが、Cdに対してはみかけ上効果がなかった

Reliability and validity of the patient disability-oriented diagnostic nomenclature system for prosthetic dentistry

Purpose: The Japan Prosthodontic Society (JPS) has proposed a new diagnostic nomenclature system (DNS), based on pathogenesis and etiology, to facilitate and improve prosthodontic treatment. This systemspecifies patient disability and the causative factor (i.e. ‘‘B (disability) caused by A (causative factor)’’). The purpose of this study was to examine the reliability and validity of this DNS. Study selection: The JPS Clinical Guideline Committee assessed mock patient charts and formulated disease names using the new DNS. Fifty validators, comprising prosthodontic specialists and dental residents, made diagnoses using the same patient charts. Reliability was evaluated as the consistency of the disease names among the validators, and validity was evaluated using the concordance rate of the disease names with the reference disease names. Results: Krippendorff’s α was 0.378 among all validators, 0.370 among prosthodontic specialists, and 0.401 among dental hospital residents. Krippendorff’s α for 10 validators (3 specialists and 7 residents) with higher concordance rates was 0.524. Two validators (1 specialist and 1 resident) with the highest concordance rates had a Krippendorff’s α of 0.648. Common disease names had higher concordance rates, while uncommon disease names showed lower concordance rates. These rates did not show correlation with clinical experience of the validator or time taken to devise the disease name. Conclusions: High reliability was not found among all validators; however, validators with higher concordance rates showed better reliability. Furthermore, common disease names had higher concordance rates. These findings indicate that the new DNS for prosthodontic dentistry exhibits clinically acceptable reliability and validity

Size Effects of High Strength Steel Wires

This study examines the effects of size on the strength of materials, especially on high strength pearlitic steel wires. These wires play a central role in many long span suspension bridges and their design, construction, and maintenance are important for global public safety. In particular, two relationships have been considered to represent strength variation with respect to length parameters: (i) the strength versus inverse square-root and (ii) inverse length equations. In this study, existing data for the strength of high strength pearlitic steel wires is evaluated for the coefficient of determination (R2 values). It is concluded that the data fits into two equations equally well. Thus, the choice between two groups of theories that predict respective relationships must rely on the merit of theoretical developments and assumptions made

Dynamic Viscosity and Transverse Ultrasonic Attenuation of Engineering Materials

In this paper, ultrasonic attenuation of the transverse waves of engineering materials is evaluated, covering metals, ceramics, polymers, fiber-reinforced plastics, and rocks. After verifying experimental methods, 273 measurements are conducted and their results are tabulated. Fifty of the tests are for the longitudinal mode. Attenuation behavior is determined over broadband spectra. The attenuation spectra are characterized in four patterns, with 2/3 of the tests showing linear frequency dependence and another ¼ linear spectrum plus Rayleigh scattering (Mason-McSkimin relation). The longitudinal and transverse damping factors varied from 0.004 to 0.065, which are 1/3 to 5 times those of polymethyl methacrylate, suggesting that almost all the engineering materials tested may be viscoelastic. The present test results make the term dynamic viscosity more appropriate for exploring the underlying processes. The observed results were compared between the longitudinal and transverse modes and among similar material types. In more than a half of the tests, the transverse attenuation coefficients were higher than the corresponding longitudinal attenuation coefficients by 1.5× or more. Some material groups had similar attenuation coefficients for the two modes. Since the physical basis for viscous damping is hardly understood, especially in hard solids, further studies from new angles are keenly desired. This collection of new attenuation data will be of value for such works. Practically, this will assist in materials selection and in designing structural health monitoring and non-destructive inspection protocols

Ultrasonic Attenuation of Carbon-Fiber Reinforced Composites

Ultrasonic attenuation measurements were conducted on cross-ply and quasi-isotropic lay-ups of eight types of carbon-fiber reinforced composites (CFRPs) using through-transmission methods with diffraction correction. Attenuation values were substantially higher than those of unidirectional composites and other structural materials. Wave modes, fiber distributions, matrix resins, and consolidation methods affected total attenuation. Transverse mode, quasi-isotropic lay-up, and polyimide and thermoplastic resins generally produced higher attenuation. No clear trends from the fiber distribution were revealed, indicating that it is not feasible presently to predict the attenuation of various lay-ups from the unidirectional values. That is, direct attenuation tests for different laminate lay-ups are needed. This work expanded the existing attenuation database by properly determining the attenuation coefficients of two additional layup types of CFRP laminates. Results showed the merit of ultrasonic attenuation measurements for quality control and structural health monitoring applications. A crucial benefit of the through-transmission methods is that they enable the prediction of Lamb wave attenuation in combination with software like Disperse (ver. 2.0.20a, Imperial College, London, UK, 2013)