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A technique of diffuse-light two-dimensional line-of-sight attenuation (diffuse 2D-LOSA) is described and demonstrated that achieves very high levels of sensitivity in transmissivity measurements (optical thicknesses down to 0.001) while effectively mitigating interferences due to beam steering. An optical system is described in which an arc lamp coupled with an integrating sphere is used as a source of diffuse light that is imaged to the center of the particulate laden medium. The center of the medium is then imaged onto a CCD detector with 1:1 magnification. Comparative measurements with collimated 2DLOSA in nonpremixed flames demonstrate the accuracy and improved optical noise rejection of the technique. Tests in weakly sooting, nonpremixed methane-air flames, and in high pressure methane-air flames, reveal the excellent sensitivity of diffuse 2D-LOSA, which is primarily limited by the shot noise of the lamp and CCD detector. OCIS codes: 120.1740, 110.6955, 120.3620, 110.0113, 120.4640, 280.2470.

We present a method based on Tikhonov regularization for solving one-dimensional inverse tomography problems that arise in combustion applications. In this technique, Tikhonov regularization transforms the ill-conditioned set of equations generated by onion-peeling deconvolution into a well-conditioned set that is less susceptible to measurement errors that arise in experimental settings. The performance of this method is compared to that of onion-peeling and Abel three-point deconvolution by solving for a known field variable distribution from projected data contaminated with an artificially generated error. The results show that Tikhonov deconvolution provides a more accurate field distribution than onion-peeling and Abel three-point deconvolution and is more stable than the other two methods as the distance between projected data points decreases. OCIS codes: 120.7000, 280.1740, 280.2470, 120.1740.

********** The prevalence of diabetes in nursing homes is 15% to l8%, which is twice as common as in the general population (1,2). The prevalence of diabetes increases with age [...], S. H. Tariq and E. Karcic are subspecialty residents for, and D. R. Thomas and C. Philpot work in, the Division of Geriatric Medicine, St. Louis University School of Medicine, St. Louis, Mo. K. Thomson and D. L. Chapel are registered dietitians at Maryland Heights Nursing Home, St. Louis, Mo. J. E. Morley is Dammert professor of gerontology, Division of Geriatric Medicine, St. Louis University School of Medicine, and the GRECC VA Medical Center St. Louis, Mo.

A technique for acquiring two-dimensional soot-volume-fraction measurements in laminar flames has been demonstrated. The technique provides a map of very low noise concentration over a range of wavelengths (250-1100 nm). A noise level of 0.0007 in extinction and a spatial resolution of 30-40 [[micro]meter] for soot concentration were achieved with an arc lamp source that was filtered to provide greater spatial coherence and a CCD detector. The broadband arc lamp source also allowed us to avoid the added noise resulting from speckle with coherent laser sources. Beam steering, due to refractive-index gradients in the flame, was measured and compared with theoretical predictions. The optical arrangement to minimize the effect of beam steering is described. As a result the beam steering had no effect on the soot measurements in the flames examined. Flame-transmission maps obtained with this system in an ethylene/air laminar diffusion flame are presented. Tomographic analysis from use of an Abel inversion of the line-of-sight data to obtain radial profiles of soot concentration is described.

Black carbon (BC) mass concentration from internal combustion engines can be quantified using a variety of different BC measurement techniques. We compare the relative response of several commercial instruments with different measurement principles to different types of marine exhaust emissions. Exhaust samples were generated using a high-speed 4-stroke marine diesel engine at various engine operating conditions from low to high engine loads. Three different fuel types—diesel, distillate marine oil grade A (DMA) and intermediate fuel oil (IFO)—were used to generate soot particles with a wide range of physical, chemical and optical properties. Based on the standard deviation of the results at all engine conditions evaluated in the present study, the overall spread between the instruments was 24% for diesel, 30% for DMA and 37% for IFO samples. For samples with extremely high organic content (at 10% engine power), the agreement was poor and the standard deviation of the mass concentrations estimated from different instruments was 50% for diesel with OC/EC ≈ 45 and 72% for DMA with OC/EC ≈280. For IFO particles, more scattered mass concentrations were reported by different instruments at all engine loads, possibly due to very complex chemical composition and different optical properties in comparison with well-characterized soot particles. We explain the differences in reported values by combining information on exhaust composition with the measurement principles used in each instrument. [ABSTRACT FROM AUTHOR]