Appearance synthesis of fluorescent objects with mutual illumination effects

We propose an approach for the appearance synthesis of objects with matte surfaces made of arbitrary fluorescent materials, accounting for mutual illumination. We solve the problem of rendering realistic scene appearances of objects placed close to each other under different conditions of uniform illumination, viewing direction, and shape, relying on standard physically based rendering and knowledge of the three-dimensional shape and bispectral data of scene objects. The appearance synthesis model suggests that the overall appearance is decomposed into five components, each of which is expanded into a multiplication of spectral functions and shading terms. We show that only two shading terms are required, related to (a) diffuse reflection by direct illumination and (b) interreflection between two matte surfaces. The Mitsuba renderer is used to estimate the reflection components based on the underlying Monte Carlo simulation. The spectral computation of the fluorescent component is performed over a broad wavelength range, including ultraviolet and visible wavelengths. We also address a method for compensating for the difference between the simulated and real images. Experiments were performed to demonstrate the effectiveness of the proposed appearance synthesis approach. The accuracy of the proposed approach was experimentally confirmed using objects with different shapes and fluorescence in the presence of complex mutual illumination effects

COrE (Cosmic Origins Explorer) A White Paper

COrE (Cosmic Origins Explorer) is a fourth-generation full-sky, microwave-band satellite recently proposed to ESA within Cosmic Vision 2015-2025. COrE will provide maps of the microwave sky in polarization and temperature in 15 frequency bands, ranging from 45 GHz to 795 GHz, with an angular resolution ranging from 23 arcmin (45 GHz) and 1.3 arcmin (795 GHz) and sensitivities roughly 10 to 30 times better than PLANCK (depending on the frequency channel). The COrE mission will lead to breakthrough science in a wide range of areas, ranging from primordial cosmology to galactic and extragalactic science. COrE is designed to detect the primordial gravitational waves generated during the epoch of cosmic inflation at more than $3\sigma$ for $r=(T/S)>=10^{-3}$. It will also measure the CMB gravitational lensing deflection power spectrum to the cosmic variance limit on all linear scales, allowing us to probe absolute neutrino masses better than laboratory experiments and down to plausible values suggested by the neutrino oscillation data. COrE will also search for primordial non-Gaussianity with significant improvements over Planck in its ability to constrain the shape (and amplitude) of non-Gaussianity. In the areas of galactic and extragalactic science, in its highest frequency channels COrE will provide maps of the galactic polarized dust emission allowing us to map the galactic magnetic field in areas of diffuse emission not otherwise accessible to probe the initial conditions for star formation. COrE will also map the galactic synchrotron emission thirty times better than PLANCK. This White Paper reviews the COrE science program, our simulations on foreground subtraction, and the proposed instrumental configuration.Comment: 90 pages Latex 15 figures (revised 28 April 2011, references added, minor errors corrected

Lidar and pressure measurements of inner-surfzone waves and setup

Author Posting. © American Meteorological Society, 2015. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Atmospheric and Oceanic Technology 32 (2015): 1945–1959, doi:10.1175/JTECH-D-14-00222.1.Observations of waves and setup on a steep, sandy beach are used to identify and assess potential applications of spatially dense lidar measurements for studying inner-surf and swash-zone hydrodynamics. There is good agreement between lidar- and pressure-based estimates of water levels (r2 = 0.98, rmse = 0.05 m), setup (r2 = 0.92, rmse = 0.03 m), infragravity wave heights (r2 = 0.91, rmse = 0.03 m), swell–sea wave heights (r2 = 0.87, rmse = 0.07 m), and energy density spectra. Lidar observations did not degrade with range (up to 65 m offshore of the lidar) when there was sufficient foam present on the water surface to generate returns, suggesting that for narrow-beam 1550-nm light, spatially varying spot size, grazing angle affects, and linear interpolation (to estimate the water surface over areas without returns) are not large sources of error. Consistent with prior studies, the lidar and pressure observations indicate that standing infragravity waves dominate inner-surf and swash energy at low frequencies and progressive swell–sea waves dominate at higher frequencies. The spatially dense lidar measurements enable estimates of reflection coefficients from pairs of locations at a range of spatial lags (thus spanning a wide range of frequencies or wavelengths). Reflection is high at low frequencies, increases with beach slope, and decreases with increasing offshore wave height, consistent with prior studies. Lidar data also indicate that wave asymmetry increases rapidly across the inner surf and swash. The comparisons with pressure measurements and with theory demonstrate that lidar measures inner-surf waves and setup accurately, and can be used for studies of inner-surf and swash-zone hydrodynamics.Funding was provided by the USACE Coastal Field Data Collection (CFDC) and Coastal Ocean Data Systems (CODS) programs, the Office of Naval Research, the National Science Foundation, and the Assistant Secretary of Defense (R&E).2016-04-0

Final report on studies of space/time variability of marine boundary layer characteristics

August 1990.Appendix A originally presented as Melanie A. Wetzel's dissertation (Colorado State University, 1990) under the title: Investigation of a remote sensing technique for droplet-effective radius.Includes bibliographical references.ONR Contract no. N00014-86-C-0459

Symmetry Detection in Large Scale City Scans

In this report we present a novel method for detecting partial symmetries in very large point clouds of 3D city scans. Unlike previous work, which was limited to data sets of a few hundred megabytes maximum, our method scales to very large scenes. We map the detection problem to a nearestneighbor search in a low-dimensional feature space, followed by a cascade of tests for geometric clustering of potential matches. Our algorithm robustly handles noisy real-world scanner data, obtaining a recognition performance comparable to state-of-the-art methods. In practice, it scales linearly with the scene size and achieves a high absolute throughput, processing half a terabyte of raw scanner data over night on a dual socket commodity PC

Experimental Investigation of Supersonic Jets Using Optical Diagnostics

The complexity of many fluid flows and phenomena is a well-known characteristic driven primarily by turbulence, which has been a focal point of study for decades. Most engineering applications in fluids will encounter turbulence, and hence the need to understand how turbulence might influence the problem at hand is omnipresent. In many turbulent flows, there are large-scale coherent structures which directly influence macro-scale processes of engineering relevance, such as noise production. Over decades of study, it has been demonstrated that similar structures are often observed across many flowfields, despite differences in characteristic parameters, and this has led to the pursuit of simplified models through the use of these dominant, shared structures. Large-scale, coherent structures are of particular importance in turbulent jets, as they represent efficient sources of sound. Noise reduction of subsonic and supersonic fluid jets represents a large interest in the study of acoustic production in jets, and much of it is viewed in the context of controlling these large-scale structures. Supersonic jets in particular may emit an intense sound known as jet screech as a consequence of these structures. This noise source easily has the potential to be damaging to both structures and humans in close proximity, and is a particular target of noise reduction efforts. Turbulent flowfields from two supersonic, underexpanded, screeching jets are analyzed by means of three non-intrusive, high-speed, optical diagnostics. The first technique is high-speed schlieren. The second technique is pulse-burst particle image velocimetry (PB-PIV). The third technique is known as focused laser differential interferometry (FLDI). Extensive spectral, statistical, and modal decomposition analyses are used in this work to identify, extract, and characterize the most energetic features and coherent structures associated with jet screech. The large field of view of the image-based datasets is fully taken advantage of by creating spatial maps of spectral and statistical quantities, which highlight regions of increased fluctuations or activity. These are shown to agree with, or demonstrate additional features that could not be reproduced by the modal analyses. Modal analyses are used to evaluate the structure of the most energetic components in the flow of both screeching jets

Comprehensive T-Matrix Reference Database: A 2007-2009 Update

The T-matrix method is among the most versatile, efficient, and widely used theoretical techniques for the numerically exact computation of electromagnetic scattering by homogeneous and composite particles, clusters of particles, discrete random media, and particles in the vicinity of an interface separating two half-spaces with different refractive indices. This paper presents an update to the comprehensive database of T-matrix publications compiled by us previously and includes the publications that appeared since 2007. It also lists several earlier publications not included in the original database

Analysis of Infragravity Frequency Sediment Transport on Macrotidal Beaches

Many cross-shore sediment transport models use simple treatments of infragravity frequency (0.005- 0.05Hz) processes. For example, infragravity waves have been assumed to provide solely a 'drift velocity' for transport of sediment mobilised by incident frequency waves (0.05-0.5Hz) and be 100% reflected at the shoreline. Furthermore, numerous models calculate broken incident wave heights on the basis of water depth only. This work investigates both the processes underlying infragravity frequency variations in the crossshore velocity field, and the resulting effect of such variations on sediment suspension and transport. Data were selected from three beach experiments in order to compare observations from a range of energetic conditions and positions in the nearshore. Experiments conducted on a dissipative beach at Llangennith, and an intermediate beach at Spurn Head, form part of the pre-existing British Beach And Nearshore Dynamics dataset. The third deployment, at a dissipative site at Perranporth (Cornwall), provided new data for analysis. At Llangennith, high swell waves (significant wave height 3m) were observed, and the measurements come from an infragravity wave dominated saturated surf zone. At Perranponh, locally generated wind wave heights were 2m and measurements came from an incident wave dominated saturated surf zone. Conditions at Spurn Head saw swell wave heights of 1.5m, and observations were made in both an incident wave dominated non-saturated surf zone and the incident wave shoaling zone. Analysis of the data revealed that, in the surf zone, the nature of the infragravity wave field was dependent upon the distribution of energy between higher (>0.02Hz) and lower (<0.02Hz) infragraviiy frequencies. Lower frequency infragravity waves were found to shoal as free waves, while higher frequency infragravity waves were dissipated near to shore on low gradient beaches. Inftagravity wave reflection coefficients showed a dependence on frequency and beach slope (parameterised by the Iribarren number), varied between 50-90% for lower infragravity frequencies, and could be less than 50% for higher infragraviiy frequencies. Incident wave heights were modulated in the shoaling zone with a 'groupy' form. Modulation was also observed in the surf zone, but in the form of individual large waves occurring at low frequency. In the shoaling zone and very close to shore, non-linear interactions occurred between the incident and infragravity components, and calculated phase values between modulated incident waves and infragravity waves indicated a phase shift from a value of less than 180° in the shoaling zone toward 0° close to shore. However, the two signals were not significantly correlated for much of the surf zone. High velocities resulting from a combination of the mean, infragravity and incident wave components drove sediment suspension. Large suspension events occurring at infragravity frequencies were correlated with incident wave groupiness in the shoaling zone, and in high energy conditions with infragravity waves near to the swash zone. Such variations in suspension were related not only to velocity magnitude, but the duration for which a threshold for suspension was exceeded. The bed response to forcing also varied during a tide, possibly as a result of changing bed conditions (e.g. due to bedforms). The infragravity contribution to suspension was independent of the magnitude of suspended sediment concentration, and increased from approximately 30% at the breaker line to 90% in an infragravity wave dominated inner surf zone. The contribution of the infragravity component to transport did not show a similar behaviour, due to phase effects, which produced a reversal in the transport direction between higher and lower infragravity frequencies. Comparison of the observations of sediment transport with energetics predictors identified several cases where the observed transport was qualitatively different from the model prediction as a result of sediment transport thresholds being exceeded at, or for, infragravity timescales