Fields radiation

Accurate modelling of the field radiated by ultrasonic transducers is an essential step forward considering the final goal of the complete simulation of pulse echo experiments. 

The Champ-Sons model has been developed to quantitatively predict the field radiated by water- or solid wedge- eoupled transdueers into solids. It is required to deal with interfaces of complex geometry, arbitrary transducers and arbitrary excitation pulses. It aims at computing the time-dependent waveform of various acoustical quantities (displacement, velocity, traction, velocity potential) radiated at a (possibly large) number of field-points inside a solid medium. 

The field radiated into the coupling medium by such a distribution of sources may be obtained by means of the well-known Rayleigh integral. The field at the considered point r is computed by a simple integral over the whole radiating surface of the contributions of each elementary source acting as a hemispherical point source. 

The Champ-Sons model is a most effieient tool allowing quantitative predictions of the field radiated by arbitrary transducers and possibly complex interfaces. It allows one to easily define the complete set of transducer characteristics (shape of the piezoelectric element, planar or focused lens, contact or immersion, single or multi-element), the excitation pulse (possibly an experimentally measured signal), to define the characteristics of the testing configuration (geometry of the piece, transducer position relatively to the piece, characteristics of both the coupling medium and the piece), and finally to define the calculation to run (field-points position, acoustical quantity considered). 

We first supposed that the field radiated into the piece by the transducer is known, thanks to the Champ-Sons model. Then, the main approximation used consists in making far field assumptions in the beam defect interaction area. In the case of a focused transducer we assume that the incident wavefronts on the defect are plane. This is equivalent to say that the defect is located in or near the transducer focal area and that a defect located outside this zone does not cause a significant echo. In the case of planar contact transducer, the incident wavefronts on the defect are assumed to be spherical The incident field on the defect is therefore approximated by the product of a spatial function gfp,0,z)describing the amplitude distribution in the beam and a time-delayed waveform < ) ft) representing the plane or spherical propagation in the beam. The incident field on the defect can therefore be approximated for ... 

Gengembre N. and Lhemery A., Transient ultrasonic fields radiated by water-coupled transducers into anisotropic solids. Review of Progress in Quantitative Non Destructive Evaluation (Plenum, New-York, 1998), to appear. 

In an attempt to reduce relapse rate and late toxicity, combined-modality therapy using lower doses of radiation and an abbreviated course of chemotherapy has been evaluated.16 The goal of decreased relapse rate has been achieved, but no overall survival benefit has been documented. A limitation of this approach is exposing patients to the additive toxicities of chemotherapy. Trials that have investigated this approach typically have incorporated between two and four cycles of a standard regimen for HL, such as ABVD (doxorubicin, bleomycin, vinblastine, and dacarbazine) with involved-field radiation. At present, combined-modality therapy is considered to be a standard of care for stage I/II HL. 

Extended-field radiation or two cycles of Stanford V or four cycles of ABVD followed by involved-field radiation... 

Options for stage I and II follicular lymphoma include locoregional radiation therapy, chemotherapy followed by radiation therapy, and extended-field radiation therapy. 

Covers charging due to relative motion or separation of two contacting phases in the absence of external electrostatic fields, radiation, or thermionic emission. The superimposition of such effects may serve to confuse the data in many cases, especially those involving natural phenomena. 

The computation of far-field radiation from a collection of incoherently radiating dipoles is in general quite a complicated problem. To calculate the angular dependence of the far-field intensity, the volume distribution of excited states must first be obtained, which, as we have seen, depends on the volume distribution of the absorbers and the electromagnetic field which stimulates them. The fields in turn depend on the frequency and linewidth of the exciting light source. Then the emission problem for the excited-state distribution (both spatial and frequency) must be solved including reorientation and depolarization effects. 

GOG-9804 Phase I/II Study of Extended Field Radiation Therapy With Concurrent Paclitaxel and Cisplatin Chemotherapy in Patients With Previously Untreated Carcinoma of the Cervix Metastatic to the Para-aortic Lymph Nodes. Study Protocol, http //www.cancer.gov/search/clinical trials... 

Kies MS, Mira JG, Crowley JJ, etal. Multimodal therapy for limited small-cell lung cancer A randomized study of induction combination chemotherapy with or without thoracic radiation in complete responders, and with wide-field vs reduced-field radiation in partial responders A Southwest Oncology Group Study. J Clin Oncol 1987 5 592-600. 

For special applications such as operation in strong magnetic fields, radiation hazard areas or in a tritium atmosphere, please contact our Technical Sates Department which has the necessary experience and which is available te you at any time. 

Extremely Low-Frequency Electric and Magnetic Fields Radiation Biology of the Skin (Beta Ray Dosimetry)... 

Interpretation of Analytical Results—Tritium. The locations of transects in the Sedan ejecta field at which samples were collected are shown in Figure 1. The distribution of tritium with depth at five sites on Sedan crater lip is shown on Figure 2. Except for the 9A area, the various sectors of the crater lip have very similar tritium depth profiles. The 9A area is a unique sector of the crater lip. A large mass of earth lifted by the detonation fell back to the crater in the 9A area earlier than the rest of the crater ejecta. Part of this material slumped into the crater, and the rest remained on the crater lip forming a prominence on the crater profile. Missile ejecta is thinner on this high point, and open-field radiation levels are lower. Tritium concentrations in the ejecta or slumped material at 9A are lower than in the rest of the crater lip mass. 

Near Field Radiation Pattern—Distribution of the irradiance over an emitting surface in other words, over the cross section of an optical waveguide. 

The discipline of radiation polymer chemistry has long been influenced by three different fields radiation physics, radiation chemistry and polymer science in theory and in their applications. 

In principle, the heat conduction can occur via near-field radiation, the gas molecules of the surrounding atmosphere, the liquid film covering tip and sample surfaces and forming a liquid bridge, or the mechanical tip-sample contact. By means of surface roughness, the effective contact area is presumed to be much smaller than the apparent (i.e. the geometric) one (Fig. 20). 

Radiation therapy is an integral part of treatment and can be used alone for selected patients with early-stage disease, although most patients wiU receive chemotherapy and radiation. Involved-field radiation therapy targets a single field of HL. Extended-field or subtotal nodal radiation targets the involved field and an uninvolved area. Total nodal radiation therapy targets aU areas. 

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