Sizing Canted Flaws in Weldments Using Low-Frequency Emats

Techniques for detecting and sizing flaws with electromagnetic-acoustic transducers (EMATs), previously used successfully for normal planar flaws, were applied to canted flaws in steel plates. Comparisons were made between metallographic and ultrasonic measurements on specially prepared welds. Results indicated a high probability of detecting canted flaws (\u3e 0.5-mm deep) with EMATs. The EMAT sizing was highly repeatable and, for the most part, very accurate. Some, as yet unexplained, inaccuracies did show up, however, in some weld sections. There is a possibility that the calibration curve may be more complex for canted flaws than for normal flaws

UT with SH-Waves and Electromagnetic Ultrasonic (EMUS) -Transducers

In the ultrasonic testing practice of today SV- and longitudinal waves are exclusively used because these wave types can be excited by piezoelectric ultrasonic transducers introduced a long time ago

Impedance of a Coil in the Vicinity of a Crack

In the design of electromagnetic NDE systems for the detection and examination of cracks and other defects in conducting materials, it is desirable to have a quantitative description of the fields in the vicinity of the defect. In previous work by this author and co-workers [1,2], the fields in the vicinity of a crack were calculated for models based on excitation by a spatially uniform applied field, as in the interior of a solenoid. The present work reports on an improved model which includes non-uniformity of the field of the exciting coil and the effects of coil size and position relative to the crack

NDE Requirements for Thick Marine Composites

There is an increasing interest in the use of thick (more than 25 mm) polymer-matrix composite materials in marine structures. At the present time, the U.S. Navy is employing state-of-the-art polymer-matrix composite materials in the construction of submarine bow domes and is interested in the use of more-advanced materials in submarine pressure hulls and specialized sonar transducers. Concurrently, there appears to be considerable interest in the commercial sector, particularly in off-shore construction, where polymer-matrix composites are used in buoyancy materials, ropes and risers

Interferometric Measurement of Ultrasonic Velocities with Line-Focusing P(VDF-TrFE) Transducer: V(f) Curves

Acoustic microscopy [1] is used to measure the V(Z) curves and thereby determine the ultrasonic velocities on the surfaces of solid materials. The acoustic transducer, point- or line-focusing, is defocused below the sample surface through the coupling water. The focal depth Z is changed to extract the interference between the specular reflection signal and the leaky surface wave signal(s). Their phase difference produces the periodic patterns of the combined amplitude as a function of Z, V(Z). The periodicity, ΔZ, together with the velocity in water and the operating frequency, gives the surface wave velocity, which is related to residual stress, preferred grain orientation (texture), or other material attribute of interest in the surface region. The V(Z) curve is an unique technique of ultrasonic NDE, because it provides a direct and localized measurement of surface wave velocities

Prevalence, awareness, treatment, and control of hypertension among United States adults 1999-2004

Detection of hypertension and blood pressure control are critically important for reducing the risk of heart attacks and strokes. We analyzed the trends in the prevalence, awareness, treatment, and control of hypertension in the United States in the period 1999-2004. We used the National Health and Nutrition Examination Survey 1999-2004 database. Blood pressure information on 14 653 individuals (4749 in 1999-2000, 5032 in 2001-2002, and 4872 in 2003-2004) aged ≥18 years was used. Hypertension was defined as blood pressure ≥140/90 mm Hg or taking antihypertensive medications. The prevalence of hypertension in 2003-2004 was 7.3±0.9%, 32.6±2.0%, and 66.3±1.8% in the 18 to 39, 40 to 59, and ≥60 age groups, respectively. The overall prevalence was 29.3%. When compared with 1999-2000, there were nonsignificant increases in the overall prevalence, awareness, and treatment rates of hypertension. The blood pressure control rate was 29.2±2.3% in 1999-2000 and 36.8±2.3% in 2003-2004. The age-adjusted increase in control rate was 8.1% (95% CI: 2.4 to 13.8%; P=0.006). The control rates increased significantly in both sexes, non-Hispanic blacks, and Mexican Americans. Among the ≥60 age group, the awareness, treatment, and control rates of hypertension had all increased significantly (P≤0.01). The improvement in blood pressure control is encouraging, although the prevalence of hypertension has not declined. © 2007 American Heart Association, Inc.link_to_OA_fulltex

UT with SH-waves and electromagnetic ultrasonic -EMUS-transducers

In the ultrasonic testing practice of today SV- and longitudinal waves are exclusively used becuse these wave types can be excited by piezoelectric ultrasonic transducers introduced a long, time ago. SH-waves offer a number of advantages compared to SV- and longitudinal waves as for example: - reflection, refraction and diffraction without mode conversion, - complete corner reflection independent of the angle of incidence, - propagation in thick-walled components (d bigger than lambda) as a bulk wave even along the surface, - propagation in thin-walled components (d smaller or equal than lambda) as a guided wave (SH-mode), - no radiation of energy into fluids of small viscosity. In principle it is possible to excite SH-waves by piezoelectric transducers, but in practice these transducers are not applicable due to coupling problems

Dancing with my mistress: embezzlement and the professionalization of banking employees in Shanghai.

Jointly organized by Chinese University of Hong Kong, Universite de Paris IV and French Centre for Research on Contemporary China