Richard G. Priest

Polarimetric microfacet scattering theory with applications to absorptive and reflective surfaces

We investigate the polarimetric scattering properties of highly absorbing and highly reflective rough surfaces in the IR. We obtain Muel- ler matrix measurements from these surfaces and compare the data to a Fresnel model. From the data, we determine that a rough, highly absorb- ing surface has a higher degree of polarization compared to a rough, highly reflective surface. In addition, we present a full polarimetric ver- sion of the microfacet model and discuss its properties. This closed-form result for the polarimetric bidirectional reflectance distribution function (BRDF) is derived from the microfacet model.

Pressure induced changes in liquid alkane chain conformation

Conformations of n‐alkane molecules in the liquid state have been studied as a function of temperature and pressure using Raman scattering. Observations of conformationally sensitive Raman bands in hexane, heptane, octane, and hexadecane reveal no sign of the pressure‐induced effects in polyethylene. Instead the Raman intensities indicate chain kinking as a function of pressure—a dramatic effect in the shorter chains, a slight effect for hexadecane. A theory based on considerations of conformational energy and translational entropy is presented which explains these effects qualitatively.

Molecular statistical model of the smectic A and smectic C phases

A molecular statistical model of the smectic A and smectic C liquid crystal phases is presented. It is found that the maximum tilt angle in the C phase is 49.1°. Free rotation about the long molecular axis is allowed in the C phase. The model allows smectic C states with chiral constitutive molecules to be ferroelectric. The second rank order parameters needed to describe a smectic C state are discussed.

Scene-based nonuniformity corrections for optical and SWIR pushbroom sensors

We propose and evaluate several scene-based methods for computing nonuniformity corrections for visible or near-infrared pushbroom sensors. These methods can be used to compute new nonuniformity correction values or to repair or refine existing radiometric calibrations. For a given data set, the preferred method depends on the quality of the data, the type of scenes being imaged, and the existence and quality of a laboratory calibration. We demonstrate our methods with data from several different sensor systems and provide a generalized approach to be taken for any new data set.

Pattern classification using projection pursuit

Abstract This article discusses the adaptation of recently developed regression techniques to classifier design. Apart from finite sample effects, projection pursuit (PP) regression may be used to model a desired response (class) as a sum of ridge functions according to a minimum expected squared error criterion. This approach can be shown to furnish an optimal discriminant function which can satisfy the Neyman-Pearson criterion over all possible thresholds. Basis function expansions are used instead of smoothed histograms to reduce computation. Since good approximation of a discriminant by a linear combination of moderate number of ridge functions may not be easy, we introduce an improved method utilizing a nonlinear weighting function.

Landau Phenomenological Theory of One and Two Component Phospholipid Bilayers

Abstract A simple phenomenological model for the excess water phospholipid bilayer main phase transition is developed. The dependence of transition temperature and latent heat on chain length is calculated. Phase diagrams for binary mixtures with components differing in chain length by 2, 4 and 6 carbons are determined. It is found that there is phase separation in the gel state for a chain length difference of 6 carbons. Comparison of theory and experiment is discussed.

Spectral and radiometric calibration of midwave and longwave infrared cameras

Accurate spectral and radiometric calibrations of IR cameras are needed to interpret infrared imagery properly, to monitor camera performance over time, and to evaluate new imaging radiometers. In this paper, the physical basis for calibrating IR cameras is derived from first principles, and a laboratory setup used to perform both radiometric and spectral calibrations is described. The calibration procedures used with this setup are then demonstrated on a midwave IR focal plane array camera, a midwave IR scanned camera, and a longwave IR scanned camera. The system spectral response and radiometric response of each camera is given and analyzed. An error analysis of approximating a cameras spectral response by an equivalent top-hat responsivity is also given.

Semiphenomenological model for the lipid bilayer phase transition: Finite chains in three dimensions

The exactly solvable model of the Nagle is reinterpreted and is used to form the basis of a Landau phenomenology of phospholipid bilayers with finite hydrocarbon chains. The properties of the model depend on the chain length. The results of the model calculation are in agreement with important experimental trends. It is found that infinite chain bilayers in the reinterpreted model should have transition temperatures of about 700 °K, while very short chain bilayers may have no phase transition.

The affine matched filter

The hyperspectral matched filter (MF) is a popular tool in remote sensing problems for locating objects that extend over several pixels. However, it is ideally suited only for the detection of sub-pixel targets with known mean signature in radiance space. Here we develop an alternative affine matched filter (AMF) that is more appropriate for detecting extended targets, and which accommodates practical uncertainties in target signature knowledge. In particular, AMF is ideal when used in conjunction with another new method we develop, called Virtual Relative Calibration (VRC), for generating a radiance space representation of a laboratory reflectance signature. VRC is related to the QUick Atmospheric Correction(QuAC) method but is much simpler. We also devise and test an extension of AMF that is meant to reduce false alarms caused by dark pixels. This Joint AMF (JAMF) expands the standard statistical model of hyperspectral backgrounds to accommodate variable illumination levels, analogously to how AMF treats target level uncertainty.

Object detection using transformed signatures in multitemporal hyperspectral imagery

Changes in atmosphere, ground conditions, and sensor response between multitemporal airborne imaging sessions have limited the use of fixed target hyperspectral libraries in helping to identify targets in heterogeneous (cluttered) backgrounds. This hyperspectral target signature instability has resulted in using anomaly detection algorithms to detect targets in real time applications. The anomaly detection algorithms, however, have not detected targets at sufficiently low false alarm rates. This study examines mathematical transforms of target spectral signatures. Specifically this study uses statistical information regarding background clutter taken from one long-wave infrared (LWIR) hyperspectral (8-12 /spl mu/m) airborne imagery flown on one day, to find the target spectral signature flown on another day (with significantly dissimilar weather conditions). The transforms use overlapping regions in the two data sets but without subpixel level registration. This work analyzes image cubes collected during the November 1998 Hyperspectral Day/Night Radiometry Assessment (HYDRA) data collect. The transformed signatures used in matched filter searches successfully find targets (even targets nearly covered) with low false alarm rates (<1 FA/kilometer/sup 2/) and remained sensitive to targets using a reduced number of pixels in the overlap region. This work has demonstrated the transformation of target spectral signatures to search for candidate targets using multitemporal hyperspectral images without requiring accurate geo-registration.