Energy-absorbing Layer Research Articles

Evaluation of Adhesive Strength of Chemical Vapor Deposition Diamond Films by Laser Spallation

The adhesive strength of polycrystalline chemical vapor deposition (CVD)-synthesized diamond films deposited on sintered SiC substrates was estimated using laser spallation. A strong pulse expansion wave was produced on the surface opposite the diamond film by the pulse laser breakdown of silicone grease confined by a silica plate and used to cause Mode-I fracture at the interface between the diamond and SiC. The amplitude of the expansion wave was monitored by a fast laser interferometer as a function of laser characteristics and the confining method. The critical laser energy for causing film spallation changed depending on the diameter of the laser beam and the thickness of the energy-absorbing layer (grease) confined by the silica plate. The driving force of the spallation was estimated to be the tensile stress of the expansion wave following the first compression wave, and it was changed significantly by the dynamics of dielectric breakdown. This was demonstrated by the waveform simulation of the out-of-plane displacement using a theoretical Green's function of the second kind for the dipole source. A pulse dipole source with short rise and decading times generates strong expansion waves.

Tumour shapes and fully automated range compensation for heavy charged particle radiotherapy

The idea of a computer-controlled range-compensating system for heavy charged particle radiotherapy, the multibar compensator, is proposed. By stacking multiple energy-absorbing layers along the beam, each of which has structure and behaviour similar to those of a multileaf collimator, variable range compensation will be achieved. The analysis of the conventional range compensators actually used for treatment concluded that the proposed system would not seriously degrade the treatment quality for the most cases, except for tumours in the head and neck region where 1 mm precision may be required. The system will even be able to coexist with the conventional range compensators to provide either method depending on clinical situations.

Surface energy absorbing layers produced by ion implantation

Single crystals of magnesia have been ion implanted with 80 keV Si − and Cr + ions at variable doses and then subjected to testing in a shock plasma. The peak surface temperature has been calibrated by measuring the size and temperature deformation of the fragments formed by multiple microcracking during thermal shock. The crack density curves for MgO crystals demonstrate that in a wide range of thermal shock intensity the ion implanted crystals develop a system of microcracks of a considerably higher density than the unimplanted ones. The high density of cracks nucleated in the ion implanted samples results in the formation of a surface energy absorbing layer which effectively absorbs elastic strain energy induced by thermal shock. As a consequence the depth of crack penetration in the layer and hence the degree of fracture damage are decreased. The results indicate that a Si implant decreases the temperature threshold of cracking and simultaneously increases the crack density in MgO crystals. However, in MgO crystals implanted with Cr a substantial increase in the crack density is achieved without a noticable decrease in the temperatutre threshold of fracture. This effect is interpreted in terms of different Cr and Si implantation conditions and damage. The mechanical properties of the energy-absorbing layer and the relation to implantation-induced lattice damage are discussed.

An approximation finite element surface impedance representation for energy absorbing layers

A procedure for determining the scattered pressure field due to a monochromatic harmonic wave that is normally incident upon an energy absorbing submerged structure is treated. The case where the structure is modeled with finite elements and the surrounding fluid is represented with either acoustic finite elements or a boundary integral approach is considered. Finite element modeling problems arise when the details of the submerged structure in the neighborhood of the fluid‐structure interface are not macroscopically homogeneous and in particular when the inhomogeneities are small relative to the acoustic wavelength. An approximate procedure is presented for replacing the detailed microscopic representation of the layered surface configuration with an equivalent simple surface impedance finite element which is specially designed to work at the frequencies of interest.

Design of a millimetre-wave ferrite isolator at 28.5 GHz

A field displacement isolator design in finline technique is described using a lamella structure including a ferrite layer, energy absorbing layers and a dielectric spacer layer. An isolator with a forward insertion loss of 1.3 dB and a reverse loss higher than 35 dB at 28.5 GHz was developed. The design was based on a field theory for the calculation of the power-density distribution inside the isolator, exact measured material parameters of the ferrite material and experimental optimisation of the lamella structure. The design procedure and the results are described in detail.

Acoustic dampening assembly for record player turntable

An acoustic dampening assembly of decoupling devices for blocking, absorbing, and deadening collision course vibrations. These decoupling devices are disposed: (a) where vibrations can be picked up by a component of the equipment from the surrounding air, (b) athwart each path of travel for vibrations through the component and particularly to and from another component, and (c) in parallel to complex resonating vibrations within associated components, for diminishing, absorbing, and blocking the transfer of such vibrations. These devices include elastomeric mounts which maintain rotating components in the rigid alignment required by design considerations, energy absorbing layers on flat surfaces, isolated sandwich cushions at points of load-bearing contact, compressing devices that produce radially-directed inward pressures, and a ballast that produces a total decoupling of the record from the turntable mechanism during play of the record.

Clamped acoustic elastic wave generator

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Pulse height defects in surface barrier detectors

Results of a study of pulse height defects in surface barrier detectors bombarded with low energy (E<500 keV) heavy ions (Z<or=18) are presented. A 'residual' energy defect is obtained after corrections for energy lost by the incident particles in the gold contact layer and to nuclear stopping. Since the behaviour of this residual energy defect does not follow that expected for a simple energy absorbing layer (supplementary entrance window) and since it shows changes correlated with depth in the detector, it appears reasonable that the residual energy defect is due mostly to carrier recombination in the sensitive zone presenting an electric field perturbation near its surface.