The entire sixteen element scattering matrix for two parallel dielectric fibers over an angular range of θ = 5°-170° as measured from the forward θ = 0 direction has been experimentally measured using the polarization modulation technique. Experimental results were in good agreement with theory for light scattering from two parallel fibers. Measurements were made for both endside and broadside illuminations at normal incidence for fibers at various separations from 2 μm to 70 μm. Laser wavelengths used were 632.8 nm and 441.2 nm, and fiber radii were 0.400±0.002 μm, 0.370±0.002 μm, 0.428±0.002 μm, and 0.406±0.002 μm. Special care was taken to measure the fiber radii, fiber separation, and to establish the parallelism between the two fibers. Electrostatic attraction between the fibers prevented the investigation for separation below 2 μm. A vibration detection device based on two-fiber light scattering has also been suggested.

No description available.

An ultrasound spectrometer was designed, constructed and used to measure the frequency dependence of forward-scattered ultrasound from biological specimens. A piezoelectric transducer was continuously tuned through the frequency range of 150 to 400 MHz, producing ultrasound of the same frequency. Pulse modulation of the input signal permitted a frequency resolution of 2 MHz. The received pulse was detected at various temporal positions of its amplitude, thereby allowing measurement of the interference of the scattered and unscattered ultrasound radiation. Because of system nonlinearities all received signals were calibrated with respect to the attenuation of ultrasound in water over the system frequency range. The attenuation of water over the frequency range of 150 to 400 MHz was consequently measured and the values agreed very well with figures given in the literature. Forward-scattering experiments were performed with both physical objects and biological specimens. Sapphire spheres and plastic cylinders exhibited the expected Mie scattering resonant structure. Planar glass plates showed the commonly observed Fabry-Perot resonant structure. Measurement of the resonant frequencies agreed well with theoretically-predicted values. The biological specimens consisted of various cell suspensions of densities on the order of 100 million cells per milliliter. Because of the high cell densities necessary for signal measurement, only signal attenuation was measured. No resonant structure was observed. Synchronized growth colonies of mouse leukemia cells were investigated at both the plateau and log stages of cell growth. The attenuation of melanoma cells was measured with and without melanin. Also, various lines of tumor cells were investigated. For all of these cell suspensions, the attenuation in dB/mm increased linearly with the logrithm of frequency. Though the slope of the attenuation-frequency curves varied from cell line to cell line, the variation for the same cells under different biological conditions was not appreciable. For all of the above cell lines, no attenuation fell out of the range of 5 to 55 dB/mm.

No description available.

The objectives of this study were to implement a system to measure mixing in nonreacting flows and to study the mass transfer characteristics of two actively excited turbulent jets. This thesis describes the acquisition and analysis of phase-locked concentration field data using planar Mie scattering from smoke particles and planar laser-induced fluorescence of acetone. Both techniques were shown to be effective in providing information for the actively excited nozzles. However, the laser-induced fluorescence technique was superior for revealing detail in the flowfield structure. Spatial mode control techniques were applied to a triangular nozzle with vibrating actuators as the three sides and a swirl nozzle with pulsating tangential air jets. The effect of the different spatial modes on jet column development and the far fields of both nozzles is presented. Two- and three-dimensional iso-intensity contours, showing the relative intensity of light scattered by the nozzle fluid marker, were generated to show the flow structure. The areas inside the iso-intensity contours in the far field were also measured to determine relative effectiveness of nozzle fluid transport. Large scale structures were visible in the three-dimensional iso-intensity contours from both nozzles. In addition, the transport of seeded nozzle fluid was enhanced by the spatial mode excitation for both nozzles. Spatial mode excitation was also able to affect the shape of the far field contour. In particular, the first counterrotating helical mode, m=±1, generated the greatest effect on nozzle fluid transport and the most pronounced elliptical contour shape in the far field. / Master of Science

Low observable technology is used in order to prevent detection, or to delay detection. Radar cross section is an important parameter in aircraft survivability since it measures how detectable an object is with radar. To find the radar cross section Maxwell's equations are solved numerically in the time-domain using a finite difference scheme. This numerical method called Finite Difference Time Domain is very suitable for structures including complex materials. However, this numerical method needs to be verified for large scale simulations, due to numerical dispersion errors. Therefore it is desirable to verify the accuracy of the numerical simulations. In this project, the analytical solution to the multiple scattering by two spheres is implemented using the T-matrix formulation. The analytical solution to the scattering problem is first validated with the analytical Mie-series solution then compared to the Finite Difference Time Domain implementation. The results imply that the difference between the numerical and analytical solution is larger for higher frequencies and larger computational volumes. / Smygteknik används för att förhindra detektering, eller för att fördröja detektion av ett flygplan. Radarmålarea är en viktig parameter för skyddsprestanda hos flygplan eftersom den mäter hur detekterbar ett föremål är med radar. För att hitta radarmålarean löses Maxwells ekvationer numeriskt i tidsdomänen med hjälp av ett finit differensschema. Den numeriska metoden som kallas Finita differensmetoden i tidsdomän, är mycket lämplig för strukturer med komplexa material. Den numeriska metoden behöver valideras för storskaliga simuleringar eftersom det förekommer felaktigheter på grund av den numeriska dispersionen. Därför är det önskvärt att kontrollera riktigheten av de numeriska simuleringarna. I detta projekt, är den analytiska lösningen till multipelspridning av två sfärer implementerad med hjälp av T-matrismetoden. Den analytiska lösningen på spridningsproblemet valideras först mot den analytiska Mie-serielösningen och sedan jämförs den med resultatet av simuleringarna med Finita differensmetoden i tidsdomän. Resultaten antyder att skillnaden mellan den numeriska och analytiska lösningen är större för högre frekvenser och större beräkningsvolymer.

The retrieval of an aerosol scattering phase function using a multi-satellite technique is proposed. A total of 33 phase functions were derived from 18 smoke cases and 15 dust cases. Each case was interrogated using four to nine satellite passes over the aerosol in a two to four hour time frame. The radiance values for the Red and Near-Infrared (NIR) channels were combined with backscattering angles to determine the shape of the scattering phase function. The radiance values were input into the Naval Postgraduate School (NPS) aerosol model to determine optical depths and sample phase functions. A comparison was made between the actual phase functions retrieved and the NPS model phase functions. It was found that the phase functions for the smoke cases more closely matched the model phase functions than in the dust cases. Some conclusions could be drawn about the actual aerosol size and density distribution based on how well it matched the model phase function. Further analysis is necessary to define the exact size and number of the aerosol particles. Fully understanding the aerosol composition is crucial in determining its effects on military sensors and impacts to operations.

Thesis (Ph. D.)--University of Washington, 1995. / Vita. Includes bibliographical references (leaves [187]-197).

Thesis (M.S. in Meteorology)--Naval Postgraduate School, March 2005. / Thesis Advisor(s): Philip A. Durkee. Includes bibliographical references (p. 77-78). Also available online.

Infrared (IR) spectroscopy has shown potential to quickly and non-destructively measure the chemical signatures of biomedical samples such as single biological cells, and tissue from biopsy. The size of a single cell (diameter ~10-50 µm) are of a similar magnitude to the mid-IR wavelengths of light (~1-10 µm) giving rise to Mie-type scattering. The result of this scattering is that chemical information is significantly distorted in the IR spectrum.Distortions in biomedical IR spectra are often observed as a broad oscillating baseline on which the absorbance spectrum is superimposed. A spectral feature commonly observed is the sharp decrease in intensity at approximately 1700 cm-1, next to the Amide I band (~1655 cm-1), which pre-2009 was called the 'dispersion artefact'. The first contributing factor towards the 'dispersion artefact' investigated was the reflection signal arising from the air to sample interface entering the collection optics during transflection experiments. This was theoretically modelled, and then experimentally verified. It was shown that IR mapping could be done using reflection mode, yielding information from the optically dense nucleus which previously caused extinction of light in transmission mode.The most important contribution to the spectral distortions was due to resonant Mie scattering (RMieS) which occurs when the scattering particle is strongly absorbing such as biomedical samples. RMieS was shown to explain both the baselines in IR spectra, and the 'dispersion artefact' and was validated using a model system of poly(methyl methacrylate) (PMMA) of varying sizes from 5 to 15 µm. Theoretical simulations and experimental data had an excellent match thus proving the theory proposed. With an understanding of the physics/mathematics of the spectral distortions, a correction algorithm was written, the RMieS extended multiplicative signal correction (RMieS-EMSC). This algorithm modelled the measured spectrum as superposition of a first guess (the reference spectrum) which was of a similar biochemical composition to the pure absorbance spectrum of the sample, and a scattering curve. The scattering curve was estimated as the linear combination of a database of a large number of scattering curves covering a range of feasible physical parameters. Simulated and measured data verified that the RMieS-EMSC increased IR spectral quality.