Perception based heterogeneous subsurface scattering for film

Many real world materials exhibit complex subsurface scattering of light. This internal light interaction creates the perception of translucency for the human visual system. Translucent materials and simulation of the subsurface scattering of light has become an expected necessity for generating warmth and realism in computer generated imagery. The light transport within heterogenous materials, such as marble, has proved challenging to model and render. The current material models available to digital artists have been limited to homogeneous subsurface scattering despite a few publications documenting success at simulating heterogeneous light transport. While the publications successfully simulate this complex phenomenon, the material descriptions have been highly specialized and far from intuitive. By combining the measurable properties of heterogeneous translucent materials with the defining properties of translucency, as perceived by the human visual system, a description of heterogeneous translucent materials that is suitable for artist use in a film production pipeline can be achieved. Development of the material description focuses on integration with the film pipeline, ease of use, and reasonable approximation of heterogeneous translucency based on perception. Methods of material manipulation are explored to determine which properties should be modifiable by artists while maintaining the perception of heterogenous translucency

Experimentation and Modeling of Laser Radiation Scattering Through Carbon Fiber Reinforced Polymers

With the prevalence of carbon fiber reinforced polymers (CFRPs) in aerospace platforms, there is a need to better understand radiative heat transport through the material. A laboratory experiment was constructed and a computational zonal Monte Carlo (ZMC) model developed to quantify and understand the laser scattering properties of CFRPs. The ZMC model builds off of the zonal method (ZM)—developed by Hottel et al. and expanded by researchers such as Yuen et al.—by incorporating Monte Carlo techniques into the ZM. The ZMC method is superior in efficiency to the ZM and alternative ray tracing methods, which enables larger mediums of exchange to be analyzed. A laser experiment was constructed using a commercial off-the shelf 1.26 kW ytterbium fiber laser (run at 70 W in this thesis) with customized optics to focus the beam into a vacuum chamber, as well as photodiodes, thermocouples, an IR camera and pyrometer for temperature, reflection and transmissivity measurements. Transmission data were analyzed using the ZMC method to determine CFRP albedo and extinction coefficients, which can be utilized for platform-level aerospace models to predict heat transfer more accurately through CFRP structures. Specifically, these optical properties can be read into multi-physics tools such as COMSOL to better predict radiation scattering through CFRP. Matching laser radiation scattering to CFRP test data has not been done before and provides validation to optical property predictions. The effects of nodal, substrate and detector plane sizing, as well as laser beam parameters, were also studied and optimized when matching albedo and extinction coefficient predictions from the ZMC method to experimental test data. Average albedo values for IM7/977-3 CFRP using the anchored ZMC method are 0.78 and 0.81 with one-ply and two-ply samples, respectively, having standard deviations of 0.11 and 0.09. Extinction coefficient predictions are 109.4 and 93.8 cm-1 with standard deviations of 28.3 and 18.8 cm-1 for one-ply and two-ply samples. When these optical properties are incorporated into multi-physic models and scaled up to larger aerospace platforms, this increased radiation transport accuracy will lead to a better understanding of laser-material interactions and burn-through times

Wireless ad-hoc networks: Strategies and Scaling laws for the fixed SNR regime

This paper deals with throughput scaling laws for random ad-hoc wireless networks in a rich scattering environment. We develop schemes to optimize the ratio, $\rho(n)$ of achievable network sum capacity to the sum of the point-to-point capacities of source-destinations pairs operating in isolation. For fixed SNR networks, i.e., where the worst case SNR over the source-destination pairs is fixed independent of $n$, we show that collaborative strategies yield a scaling law of $\rho(n) = {\cal O}(\frac{1}{n^{1/3}})$ in contrast to multi-hop strategies which yield a scaling law of $\rho(n) = {\cal O}(\frac{1}{\sqrt{n}})$. While, networks where worst case SNR goes to zero, do not preclude the possibility of collaboration, multi-hop strategies achieve optimal throughput. The plausible reason is that the gains due to collaboration cannot offset the effect of vanishing receive SNR. This suggests that for fixed SNR networks, a network designer should look for network protocols that exploit collaboration. The fact that most current networks operate in a fixed SNR interference limited environment provides further motivation for considering this regime.Comment: 26 pages single column, submitted to Transactions on Information Theor

Fundamental remote sensing science research program. Part 1: Scene radiation and atmospheric effects characterization project

Brief articles summarizing the status of research in the scene radiation and atmospheric effect characterization (SRAEC) project are presented. Research conducted within the SRAEC program is focused on the development of empirical characterizations and mathematical process models which relate the electromagnetic energy reflected or emitted from a scene to the biophysical parameters of interest

RNA reference materials with defined viral RNA loads of SARS-CoV-2—A useful tool towards a better PCR assay harmonization

SARS-CoV-2, the cause of COVID-19, requires reliable diagnostic methods to track the circulation of this virus. Following the development of RT-qPCR methods to meet this diagnostic need in January 2020, it became clear from interlaboratory studies that the reported Ct values obtained for the different laboratories showed high variability. Despite this the Ct values were explored as a quantitative cut off to aid clinical decisions based on viral load. Consequently, there was a need to introduce standards to support estimation of SARS-CoV-2 viral load in diagnostic specimens. In a collaborative study, INSTAND established two reference materials (RMs) containing heat-inactivated SARS-CoV-2 with SARS-CoV-2 RNA loads of ~107 copies/mL (RM 1) and ~106 copies/mL (RM 2), respectively. Quantification was performed by RT-qPCR using synthetic SARS-CoV-2 RNA standards and digital PCR. Between November 2020 and February 2021, German laboratories were invited to use the two RMs to anchor their Ct values measured in routine diagnostic specimens, with the Ct values of the two RMs. A total of 305 laboratories in Germany were supplied with RM 1 and RM 2. The laboratories were requested to report their measured Ct values together with details on the PCR method they used to INSTAND. This resultant 1,109 data sets were differentiated by test system and targeted gene region. Our findings demonstrate that an indispensable prerequisite for linking Ct values to SARS-CoV-2 viral loads is that they are treated as being unique to an individual laboratory. For this reason, clinical guidance based on viral loads should not cite Ct values. The RMs described were a suitable tool to determine the specific laboratory Ct for a given viral load. Furthermore, as Ct values can also vary between runs when using the same instrument, such RMs could be used as run controls to ensure reproducibility of the quantitative measurements.Peer Reviewe

Optical and Chemical Response of Nanostructured Films

When illuminated with visible light, nanostructured noble metals exhibit a strongplasmon resonance at wavelength, p, that has been shown to be sensitive to its size,structure, the dielectric properties of the surrounding medium, and charge density. Thetunability of the plasmon resonance has allowed metal nanosystems to be fabricated withresonances matching the solar spectrum for us in plasmon promoted catalysis, plasmonicphotovoltaics, and surface-enhanced raman spectroscopy. Here we use UV-Visible spectroscopyto track the shifts of the plasmon resonances from an array of gold nanoparticlesburied under metal oxide layers of varying thickness when in contact with one of two bulkmetals: aluminum or silver. By assuming the array of gold nanoparticles and metal-oxidelayers to be an optically homogenous lm of core-shell particles on a substrate, we developeda Maxwell-Garnett effective medium approximation to extract reliable opticalparameters for the gold nanoparticles, yielding their charge state before and after contactwith the bulk metal.Based on the optical parameters extracted from our model, we nd the magnitude ofcharge transfer from the bulk metal to the gold nanoparticle is independent of the workfunction of the bulk metal. Furthermore, when gold is used as the bulk layer in contactwith the gold nanoparticles, we measured an appreciable amount of charge transfer to thegold nanoparticles, failing to support the well-established model for electrostatic contactelectrication. Instead, we attribute the charge transfer to the so called plasmoelectriceffect, an optically induced charge transfer mechanism, in which the gold nanoparticlemodifes its charge density to allow its resonant wavelength to match that of the incidentlight. We show, however, that in our devices the Schottky barriers between the metalsand the metal oxide layers create a rectication effect that favors electron transfer fromthe bulk metal to the nanoparticles over the reverse effect

Design and Development of Heterogenous Combustion Systems for Lean Burn Applications

Combustion with a high surface area continuous solid immersed within the flame, referred to as combustion in porous media, is an innovative approach to combustion as the solid within the flame acts as an internal regenerator distributing heat from the combustion byproducts to the upstream reactants. By including the solid structure, radiative energy extraction becomes viable, while the solid enables a vast extension of flammability limits compared to conventional flames, while offering dramatically reduced emissions of NOx and CO, and dramatically increased burning velocities. Efforts documented within are used for the development of a streamlined set of design principles, and characterization of the flame\u27s behavior when operating under such conditions, to aid in the development of future combustors for lean burn applications in open flow systems. Principles described herein were developed from a combination of experimental work and reactor network modeling using CHEMKIN-PRO. Experimental work consisted of a parametric analysis of operating conditions pertaining to reactant flow, combustion chamber geometric considerations and the viability of liquid fuel applications. Experimental behavior observed, when utilizing gaseous fuels, was then used to validate model outputs through comparing thermal outputs of both systems. Specific details pertaining to a streamlined chemical mechanism to be used in simulations, included within the appendix, and characterization of surface area of the porous solid are also discussed. Beyond modeling the experimental system, considerations are also undertaken to examine the applicability of exhaust gas recirculation and staged combustion as a means of controlling the thermal and environmental output of porous combustion systems. This work was supported by ACS PRF 51768-ND10 and NSF IIP 1343454