[en] A method to measure the resonance frequency of the ultrasonic transducer which is adhered to the specimen by the ultrasonic visualization is tried. The result shows that the resonance frequency of the transducer adhered to the specimen is lower than the nominal resonance frequency of the transducer in itself and the greater the degree of deviation. It is verified that its cause is the resonance of Al-plate for protecting the transducer by the theoretical analysis

[en] We present a homogenization model for a single row of locally resonant inclusions. The resonances, of the Mie type, result from a high contrast in the shear modulus between the inclusions and the elastic matrix. The presented homogenization model is based on a matched asymptotic expansion technique; it slightly differs from the classical homogenization which applies for thick arrays with many rows of inclusions (and thick means large compared to the wavelength in the matrix). Instead of the effective bulk parameters found in the classical homogenization, we end up with interface parameters entering in jump conditions for the displacement and for the normal stress; among these parameters, one is frequency dependent and encapsulates the resonant behavior of the inclusions. Our homogenized model is validated by comparison with results of full wave calculations. It is shown to be efficient in the low frequency domain and accurately describes the effects of the losses in the soft inclusions. (authors)

[en] Complete text of publication follows. Since electromagnetic (EM) signals generated by fault rupture travel at the speed of light, signals generated by initial preseismic fault rupture and subsequent rupture with associated seismic radiation arrive with negligible delay at surface observation sites. This contrasts with the inherent time delays plaguing observations of rupture and radiation recorded on near-surface seismic and strain instrumentation since these propagate more slowly at seismic wave speeds (Vp∼5 km/s, Vs∼2 km/s). Observation of EM during earthquake nucleation and rupture evolution could provide unique information about the earthquake source size and rupture evolution before the first P wave arrivals, if these EM signals can be detected. While clear observations of the magnetic offsets resulting from the total stress change with earthquakes have been frequently obtained, EM data showing rupture initiation before radiation starts (i.e. before the earthquake origin time) and during rupture evolution have been difficult to identify. Nevertheless, the magnetic offset data produced by the earthquake allow direct scaling to the largest allowable slip moment (modulus x area x slip) during both nucleation prior to rupture and rupture evolution after initiation. For the 2004 M6 Parkfield earthquake where 40 sample/sec EM observations were recorded through the earthquake at a point about 4 km above the final rupture and 15 km from the earthquake hypocenter, we observe less than 30 pT during the seconds prior to rupture initiation and 25 pT from rupture initiation to the first P wave arrival. This constrains the earthquake nucleation moment and rupture evolution moment to less than 2x10¹⁶ Nm (i.e. a moment magnitude less than that of a M5 earthquake).

[en] This paper proposes an ultrasonic method for measurement of linear and hysteretic interfacial stiffness of contacting surfaces between two steel plates subjected to nominal compression pressure. Interfacial stiffness was evaluated by the reflection and transmission coefficients obtained from three consecutive reflection waves from solid-solid surface using the shear wave. A nonlinear hysteretic spring model was proposed and used to define the quantitative interfacial stiffness of interface with the reflection and transmission coefficients. Acoustic model for 1-D wave propagation across interfaces is developed to formulate the reflection and transmission waves and to determine the linear and nonlinear hysteretic interfacial stiffness. Two identical plates are put together to form a contacting surface and pressed by bolt-fastening to measure interfacial stiffness at different states of contact pressure. It is found from experiment that the linear and hysteretic interfacial stiffness are successfully determined by the reflection and transmission coefficient at the contact surfaces through ultrasonic pulse-echo measurement.

[en] Ultrasound (US) elastography has been introduced as a non-invasive technique for evaluating thyroid diseases. This paper presents a detailed description of the technical principles, peculiarities, and limitations of US elastography techniques, including strain elastography and shear-wave elastography. This review was conducted from a clinical perspective, and aimed to assess the usefulness of US elastography for thyroid diseases in specific clinical scenarios. Although its main focus is on thyroid nodules, the applications of US elastography for other thyroid diseases, such as diffuse thyroid diseases and thyroiditis, are also presented. Furthermore, unresolved questions and directions for future research are also discussed

[en] A method and apparatus for shear wave logging which utilizes relatively high frequency sweep control transmission and subsequent correlation of received signals in order to define travel times of horizontally polarized shear and/or torsional wave energy. The apparatus includes specific sonde structure for effecting firm contact of transmitting and receiving elements with the borehole wall

[en] The refraction seismic method was applied to investigate subsurface geological structure by analyzing recoded first arrivals of P-wave to determine the seismic velocity and estimate thickness of weathering layer and depth of overlaid wadi the velocity model was generated by using time-term inversion and tomographic inversion as alternative technique used in complicated geological structures subsurface structure was determined and detailed information about horizontal and vertical of seismic velocity was found by using tomographic inversion method the calculated velocity (VP) equals to 400m/s for weathered layer and 1000m/s for second layer. The second layer most probably consists of dry sands and the thickness of weathered layer was about (1.3-4.9m) comparing the results with the nearby borehole tests ensures the precision of the used method and discussion. (author)

[en] The purpose of this study was to compare the technical success rate and reliability of measurements made using three shear wave elastography (SWE) techniques and to assess the inter-platform reproducibility of the resultant liver stiffness measurements. This prospective study included 54 patients with liver disease. Liver stiffness (LS) measurements were obtained using 2-point SWE techniques (Virtual Touch Quantification and S-Shearwave) and 2-dimensional (2D) SWE, with transient elastography (TE) serving as the reference standard. The technical success rates and measurement reliability of the three techniques were compared. LS values measured using the three SWE techniques and TE were compared using Spearman correlation coefficients and 95% Bland-Altman limits of agreement. Intra-class correlation coefficients (ICC) were used to analyze the inter-platform reproducibility of LS measurements. The three SWE techniques and TE showed similar technical success rates (P=0.682) but demonstrated significant differences in the reliability of LS measurements (P=0.006) and mean LS measurements (P<0.001). Despite strong correlations (r=0.73-0.94) between SWE systems, various degrees of inter-platform reproducibility (ICC, 0.58-0.92) were observed for the three SWE techniques. The best agreement was observed between S-Shearwave and TE (ICC, 0.92), and the worst agreement was observed between 2D-SWE and TE (ICC, 0.58). In the Bland-Altman analysis, a tendency toward lower LS values with the three SWE techniques than with TE in patients with F3 and F4 disease was observed. Significant inter-system variability was observed in LS measurements made using the three SWE techniques. Therefore, LS values measured using different SWE techniques should not be used interchangeably for longitudinal follow-up

[en] New data on geodynamic process in the area of North Tien Shan, revealed earlier based in anomaly absorption of seismic waves, is being analyzed. It was established that here for last 5-7 years (since 1999 till 2005) features of S-wave absorption field in earth crust and upper mantle within anomaly area had been significantly changed - new elliptic structure had been formed, generated by focuses of relatively deep earthquakes. Within the boundaries of this area in 2005, earthquakes with mechanism of normal faulting and oblique normal prevailed. Amount of the obtained data indicate active increase of juvenile fluids in earth crust and in upper mantle within anomaly area that may testify preparation of a strong earthquake ( ∼6.5). (author)

[en] Complete text of publication follows. Most of reported geomagnetic field changes at the time of earthquakes are 'coseismic' step-like offsets in the geomagnetic field, which are regarded as the piezomagnetic effect caused by stress changes due to earthquake faulting (Stacey, 1964). Proton precession magnetometers have so far been mainly used to detect the seismomagnetic effect, of which measurement interval was usually 1 or 10 minutes and measurement accuracy was 0.1 nT. For seismomagnetic observations we employed this time flux-gate magnetometers whose specifications are the measurement with accuracy of 0.01 nT and with the sampling interval of 0.5 or 1 sec. By virtue of such highly sensitive magnetometers, we observed the co-seismic magnetic signals accompanied with the fault movement. Our observation site happened to be situated at an epicentral distance of 26 km from the June 14, 2008 Iwate-Miyagi Nairiku earthquake of M 7.2, NE Japan. Magnetic field components began to change almost simultaneously with the onset of the earthquake to grow up monotonously until the first P wave arrival. Such coseismic magnetic signals are most probably generated by the growing stress field due to faulting, i.e. the piezomagnetic effect, rather than the seismic dynamo effect (Honkura et al., 2002) or electromagnetic induction within the conducting crust. This is because they lack oscillatory features like seismic waves. We attempt to interpret the observations with the aid of static piezomagnetic models (Utsugi et al., 2000).