A Computationally Efficient Modeling Code for Sh-Waves in Austenitic Welds Using an Explicit Space-Time Green-Function

For ultrasonic inspection of austenitic welds and cladded components horizontally polarized shear (SH) waves — as generated by electromagnetic acoustic transducers (EMATs) — have certain benefits compared with quasi-vertically polarized shear and quasi-pressure waves. SH-waves suffer the least distortion of all three wave modes when propagated through anisotropic weld material and no energy is lost through mode conversion at the steel/free surface or base metal/weld interfaces. To explain experimentally observed phenomena and to predict the cases where SH-waves might be best employed, modeling of the respective wave propagation effects is useful. In this contribution, a computationally efficient modeling code is presented for SH-waves propagating in transversely isotropic media, thus particularly applicable to ideally fiber-textured austenitic weld material. An explicit space-time domain far-field representation of Green’s dyadic function has been derived with respect to the wave type under concern, the fiber direction being included as a free parameter. The obtained relationships have been applied to the Generalized Point-Source-Synthesis method (GPSS [1,2]) to model radiation, propagation and scattering effects. The code thus improved — SH-GPSS— is characterized by a considerable reduction of computer run-time and is therefore particularly convenient in view of a respective extension to inhomogeneous weldments. Numerical results are presented for both continuous wave and time-dependent rf-impulse modeling for austenitic weld metal specimens, covering field profiles as well as wave front snapshots for a phased array EMAT-probe

Pathogenesis of sudden death following water immersion (immersion syndrome)

Sympathetic activity under cold stress is investigated. Predominantly vagal cardio-depressive reflexes are discussed besides currently known mechanisms of sudden death after water immersion. Pronounced circulatory centralization in diving animals as well as following exposure in cold water indicates additional sympathetic activity. In cold water baths of 15 C, measurements indicate an increase in plasma catecholamine levels by more than 300 percent. This may lead to cardiac arrhythmias by the following mechanisms: cold water essentially induces sinus bradycardia; brady-and tachycardiarrhythmias may supervene as secondary complications; sinusbradycardia may be enhanced by sympathetic hypertonus. Furthermore, ectopic dysrhythmias are liable to be induced by the strictly sympathetic innervation of the ventricle. Myocardial ischemia following a rise in peripheral blood pressure constitutes another arrhythmogenic factor. Some of these reactions are enhanced by alcohol intoxication

Excitation Optimization of a Standard LRC Circuit with Impulsive Forces Selected via Simulated Annealing

For an unknown oscillator, it is sometimes useful to know what the potential energy function associated with it is. An argument for using a method of determining the optimal sequence of impulsive forces in order to find the potential energy function is made using principles of energy. Global optimization via simulated annealing is discussed, and various parameters that can be adjusted across experiments are established. A method for determining the optimal sequence of impulsive forces for the excitation of a standard LRC circuit is established using the methodology of simulated annealing

Die problematiek verbonde aan die maatskaplike hantering van die gemolesteerde kind

Sexual moleslation is most certainly the phenomenon that evokes most repulsion in society at large, and in the helping professions. Since this phenomenon has been exposed by various sources, it is clear at present that professional institutions or people are still not successfully geared to render a non-fragmented service to the culprit, the victim and their various families. It would appear that, when services are rendered, the various professions involved in the case are not clear with regard to their various roles. Not only does a lack of knowledge exist regarding the phenomenon dealt with, hut also regarding the legal process that is mostly involved in these cases. Almost no identified resource exists in the community which one can approach for help without the emphasis on prosecution. This may enhance the possibility that cases still be kept secret. The question may be asked whether prosecution should be the way to handle sexual molestation, a process during which the involved child cannot he fully protected. Should other forms o f help-rendering not be considered

Results on Transversal and Axial Motions of a System of Two Beams Coupled to a Joint through Two Legs

In recent years there has been renewed interest in inflatable-rigidizable space structures because of the efficiency they offer in packaging during boost-to-orbit. However, much research is still needed to better understand dynamic response characteristics, including inherent damping, of truss structures fabricated with these advanced material systems. We present results of an ongoing research related to a model consisting of an assembly of two beams with Kelvin-Voight damping, coupled to a simple joint through two legs. The beams are clamped at one end but at the other end they satisfy a boundary condition given in terms of an ODE coupling boundary terms of both beams, which reflects geometric compatibility conditions. The system is then written as a second order differential equation in an appropriate Hilbert space  in which well-posedness, exponential stability as well as other regularity properties of the solutions can be obtained. Two different finite dimensional approximation schemes for the solutions of the system are presented. Numerical results are presented and comparisons are made.Fil: Burns, J. A.. Interdisciplinary Center for Applied Mathematics; Estados UnidosFil: Cliff, E. M.. Interdisciplinary Center for Applied Mathematics; Estados UnidosFil: Liu, Z.. University of Minnesota at Duluth; Estados UnidosFil: Spies, Ruben Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Matemática Aplicada del Litoral. Universidad Nacional del Litoral. Instituto de Matemática Aplicada del Litoral; Argentin

COLUMBIA MEDICAL CENTER AND THE COCAINE ADDICTED PHARMACIST (A)

Tom Zenor, a pharmacist for Columbia Medical Center, became addicted to cocaine. He checked himself into a rehabilitation center and, upon request, was placed on leave as allowed by the Family Medical Leave Act (FMLA). During his FMLA leave the company decided to terminate his employment upon the completion of his twelve week leave of absence. Columbia, in an attempt to be proactive, is considering any legal recourse Zenor might attempt. Columbia’s Human Resources manager, Carmen Estrada, is preparing evidence to defend the company against a potential Americans with Disabilities Act (ADA) lawsuit. Her primary concern is that Zenor will claim that his cocaine addiction is a qualified disability under the ADA. (Contact author for a copy of the complete report.)Personnel, Unjust Termination, At-Will Employment

Columbia Medical Center and the Cocaine-Addicted Pharmacist: Unjust Termination? (B)

Tom Zenor, a pharmacist for Columbia Medical Center, became addicted to cocaine. He checked himself into a rehabilitation center and, upon request, was placed on leave as allowed by the Family Medical Leave Act (FMLA). Upon his return, the company decided to terminate his employment. Zenor was upset at the dismissal, which he saw as unjust. Columbia Medical Center, in an attempt to be proactive, sought to consider any legal recourse Zenor might attempt. Columbia’s Human Resources manager, Carmen Estrada, attempted to construct evidence to defend the company against a potential unjust discharge case. The company operated in Texas, which was an “at-will” state. Nonetheless, Estrada had concerns which included whether Zenor could claim an exception to the Doctrine of Employment at-will, and if including a disclaimer in an employee handbook that employees are retained “at-will” provided adequate legal protection for the organization. (Contact author for a copy of the complete report.)Personnel, Addiction, ADA

Application-Directed Modeling of Radiation and Prpagation of Elastic Waves in Anisotropic Media: GPSS and OPOSSM

In ultrasonic nondestructive testing use is made of the physical properties of elastic waves in solids in order to detect defects and material inhomogeneities. Difficulties in testing anisotropic materials are due to the direction dependence of the ultrasonic velocities and to the inherent effects of beam divergence and beam distortion. Based on a theory of elastic wave propagation in transversely isotropic media [1], the Generalized Point-Source-Synthesis-method (GPSS) has been developed to model the radiation, propagation and scattering of elastic waves as generated by ultrasonic transducers in these media [2]. The method accounts for the three-dimensionality and the vectorial character of anisotropic wave phenomena and is particularly useful in view of application-directed modeling at low computation times. A specifically interesting outcome is OPoSSM (‘Optimization by Point-Source-Synthesis-Modeling’), which allows optimized dimensioning and build-up of complex transducers according to their selected field of application. In this contribution, results are presented for austenitic weld material and fiber composites, covering echo dynamic curves — in comparison with experimental results — for commercial transducers. Furthermore, OPoSSM-results on optimized TR-array-probes are presented as well as snapshots of transducer-generated wavefronts, impressively illustrating the modeling of time-dependent rf-signals