Assessing the contributions of surface waves and complex rays to far-field Mie scattering by use of the Debye series

The contributions of complex rays and the secondary radiation shed by surface waves to scattering by a dielectric sphere are calculated in the context of the Debye series expansion of the Mie scattering amplitudes. Also, the contributions of geometrical rays are reviewed and compared with the Debye series. Interference effects between surface waves, complex waves, and geometrical waves are calculated, and the possibility of observing these interference effects is discussed. Experimental data supporting the observation of a surface wave-geometrical pattern is presented

The internal caustic structure of illuminated liquid droplets

The internal electric field of an illuminated liquid droplet is studied in detail using both wave theory and ray theory. The internal field obtains its maximum values on the caustics within the droplet. Ray theory is used to determine the equations of these caustics and the density of rays on them. The Debye series expansion of the interior field Mie amplitudes is used to calculate the wave theory version of these caustics. The physical interpretation of the sources of stimulated Raman scattering and fluorescence emission within a liquid droplet is then given

Gateways Not Pathways: Student Perceptions of the Portals to Employability

The expectation that tertiary education leads to employment is one that most commencing students hold. A problem arises when there is a gap between the knowledge and skills students expect to acquire and the knowledge and skills course designers and teachers expect students to develop. The present study interviewed 22 first year students and 12 final year students to explore their expectations and experiences of employability teaching and learning, and compared these to the conceptions of employability articulated in their institution’s policy documentation. The findings suggest that most students believed that, to achieve their career goals, their primary focus should be on completing their academic studies, and that all relevant knowledge and skills would be unveiled during this process. As such, they viewed their time at university as a distinct stage in their development, one that must be completed before they move on to engage with the challenge of employment. Such expectations differ in important ways from those of the institution at which participants were enrolled, which sets employability within the context of an ever-changing job market and the consequent need for life-long learning. Moreover, while the institution clearly articulates the skills that they believe are embedded within their units and courses, this is not being conveyed to students. Implications of this research highlight the need to carefully consider what expectations students are bringing with them regarding the enhancement of employability and how institutions can best act to bridge the gap between students’ expectations and their own

Experimental testing of four correction algorithms for the forward scattering spectrometer probe

Three number density correction algorithms and one size distribution correction algorithm for the Forward Scattering Spectrometer Probe (FSSP) were compared with data taken by the Phase Doppler Particle Analyzer (PDPA) and an optical number density measuring instrument (NDMI). Of the three number density correction algorithms, the one that compared best to the PDPA and NDMI data was the algorithm developed by Baumgardner, Strapp, and Dye (1985). The algorithm that corrects sizing errors in the FSSP that was developed by Lock and Hovenac (1989) was shown to be within 25 percent of the Phase Doppler measurements at number densities as high as 3000/cc

A Correction Algorithm for Particle-Size Distribution Measurements Made with the Forward-Scattering Spectrometer Probe

Multiparticle coincidence events in the scattering volume of the forward-scattering spectrometer probe (FSSP) cause the instrument to bias the measurement of the particle size distribution of atmospheric aerosols toward large diameters. We employ a probabilistic model based on Poisson statistics to determine the average diameter and rms width of the actual size distribution as functions of the average diameter and rms width of the measured distribution. We compare our predictions to a Monte Carlo simulation of the FSSP operatio

Assessing the Contributions of Surface Waves and Complex Rays to Far-Field Mie Scattering by Use of the Debye Series

The contributions of complex rays and the secondary radiation shed by surface waves to scattering by a dielectric sphere are calculated in the context of the Debye-series expansion of the Mie scattering amplitudes. Also, the contributions of geometrical rays are reviewed and compared with those of the Debye series. Interference effects among surface waves, complex rays, and geometrical rays are calculated, and the possibility of observing these interference effects is discussed. Experimental data supporting the observation of a surface-wave-geometrical-ray-interference pattern are presented

An Improved Correction Algorithm for Number Density Measurements Made with the Forward-Scattering Spectrometer Probe

A correction factor to the number density measured by the Forward Scattering Spectrometer Probe (FSSP) which compensates for dead time and coincidence errors was determined by calculating the probabilities of and the average number of particles in the six possible types of dead time and coincidence events. These probabilities and averages were calculated by means of a probabilistic model based on Poisson statistics. A Monte Carlo computer simulation of the FSSP operation was also carried out and the number density correction factor was compared with the Monte Carlo data. For an actual number density of 2000/cm3, it was found that the measured number density was of the order of 300/cm3

Internal Caustic Structure of Illuminated Liquid Droplets

The internal electric field of an illuminated liquid droplet is studied in detail with the use of both wave theory and ray theory. The internal field attains its maximum values on the caustics within the droplet. Ray theory is used to determine the equations of these caustics and the density of rays on them. The Debye-series expansion of the interior-field Mie amplitudes is used to calculate the wave-theory version of these caustics. The physical interpretation of the sources of stimulated Raman scattering and fluorescence emission within a liquid droplet is then given

Internal Caustic Structure of Illuminated Liquid Droplets

The internal electric field of an illuminated liquid droplet is studied in detail with the use of both wave theory and ray theory. The internal field attains its maximum values on the caustics within the droplet. Ray theory is used to determine the equations of these caustics and the density of rays on them. The Debye-series expansion of the interior-field Mie amplitudes is used to calculate the wave-theory version of these caustics. The physical interpretation of the sources of stimulated Raman scattering and fluorescence emission within a liquid droplet is then given

Laser diffraction particle sizing: Instrument probe volume relocation and elongation

The effective probe volume of laser diffraction particle sizing instruments depends on many instrument parameters. In particular the probe volume axial boundaries and its location along laser beam are essentially defined by the onset of a vignetting effect where light scattered at large angles from small particles misses the transform lens. This vignetting effect results in a probe volume that must be inconveniently close to the lens in order to detect smaller diameter particles (less than 100 micrometers). With the addition of an appropriately designed Keplerian telescope, the probe volume may be relocated and elongated. The theory of operation of this supplemental optical system is described. Design considerations for these supplemental optical systems are described, including recommendations for lens specifications, assembly and use. An image transfer system is described which has been designed for use on a Malvern 2600HSD instrument. Experimental validation of this image transfer system is described