Relative Position Of Source Research Articles

In vivo measurement of the optical interaction coefficients of human tumours at 630 nm

The light distribution within a treatment volume is determined by the source geometry (e.g. superficial or interstitial illumination) and the optical interaction coefficients of the irradiated tissue. The authors have measured the energy fluence rate at various points within tumours undergoing irradiation with 630 nm light for photodynamic therapy for several source geometries. The relative positions of source and detector fibres were determined using CT scanning techniques. The results of the measurements were then applied to solutions of the diffusion theory which allowed the determination of the absorption coefficient ( Sigma a=30.5+or-16 m-1), the reduced scattering coefficient ( Sigma s=941+or-735 m-1), the effective attenuation coefficient ( Sigma eff=261+or-49 m-1) and the build-up coefficient which relates surface irradiance to the energy fluence rate at depth (k=1.6+or-0.6).

Scholte wave generation by vertically guided waves in steep topographic feature

Interaction of underwater acoustic waves with the Arctic ice cover is least understood when the wavelength is comparable to ice thickness and topographic feature dimensions. Generation and detection of Scholte waves along a flat water/ice interface require proximity of both source and receiver to the ice. Laboratory ultrasonic experimental results are presented demonstrating the generation of pulsed broadband Scholte waves at ice/water interfaces from interaction of remote underwater source with a single steep ice topographic feature. Examples are given from different bonded ice ridges and unattached floating scatterers near the interface. The effects of ridge height, ridge width, and relative source position on the generation of Scholte waves are revealed. Each topographic feature acts as a vertical acoustic waveguide and locally excites the ice/water interface. Focusing of guided waves by ridge geometry enhances the generation of Scholte waves. The results also provide physical insight into the excitati...

DESIGN OF PARTIAL PARTITIONS FOR SCHOOL BUILDINGS IN ASIA

Summary A comprehensive study was undertaken under UNESCO/ARISBR sponsorship of the acoustical conditions in several school buildings of Ceylon, India, Malaysia and Singapore and of noise reduction by some typical flexible partitions. These partitions are used for dividing teaching spaces. Consequently, the minimum height of the partition between two teaching spaces, the material of the partition, position of the chalk board etc. were some of the important factors which were drawn from this study. The study led to the conclusion that the most important factors ahich decide about the partition are the prevailing nature of sound field in the class room and relative position of source and receiver with reference to the screen, whereas material of the screen as well as the height of the screen are not found to be very important. The desired values of the various parameters have been decided as a result of the study conducted by the authors in the above survey in which values of speech articulation index, intr...