NOSS altimeter algorithm specifications

A description of all algorithms required for altimeter processing is given. Each description includes title, description, inputs/outputs, general algebraic sequences and data volume. All required input/output data files are described and the computer resources required for the entire altimeter processing system were estimated. The majority of the data processing requirements for any radar altimeter of the Seasat-1 type are scoped. Additions and deletions could be made for the specific altimeter products required by other projects

Tunability of the optical absorption in small silver cluster-polymer hybrid systems

We have calculated the absorption characteristics of different hybrid systems consisting of Ag, Ag2 or Ag3 atomic clusters and poly(methacrylic acid) (PMAA) using the time-dependent density-functional theory. The polymer is found to have an extensive structural-dependency on the spectral patterns of the hybrid systems relative to the bare clusters. The absorption spectrum can be `tuned' to the visible range for hybrid systems with an odd number of electrons per silver cluster, whereas for hybrid systems comprising an even number of electrons, the leading absorption edge can be shifted up to about 4.5 eV. The results give theoretical support to the experimental observations on the absorption in the visible range in metal cluster-polymer hybrid structures.Comment: Updated layout and minor changes in versions 2 and

Inelastic X-ray scattering from valence electrons near absorption edges of FeTe and TiSe2_2

We study resonant inelastic x-ray scattering (RIXS) peaks corresponding to low energy particle-hole excited states of metallic FeTe and semi-metallic TiSe$_2$ for photon incident energy tuned near the $L_{3}$ absorption edge of Fe and Ti respectively. We show that the cross section amplitudes are well described within a renormalization group theory where the effect of the core electrons is captured by effective dielectric functions expressed in terms of the the atomic scattering parameters $f_1$ of Fe and Ti. This method can be used to extract the dynamical structure factor from experimental RIXS spectra in metallic systems.Comment: 6 pages, 4 figure

Elliptic Phases: A Study of the Nonlinear Elasticity of Twist-Grain Boundaries

We develop an explicit and tractable representation of a twist-grain-boundary phase of a smectic A liquid crystal. This allows us to calculate the interaction energy between grain boundaries and the relative contributions from the bending and compression deformations. We discuss the special stability of the 90 degree grain boundaries and discuss the relation of this structure to the Schwarz D surface.Comment: 4 pages, 2 figure

The Impact of Postures and Moving Directions in Fire Evacuation in a Low-Visibility Environment

Walking speed is a significant aspect of evacuation efficiency, and this speed varies during fire emergencies due to individual physical abilities. However, in evacuations, it is not always possible to keep an upright posture, hence atypical postures, such as stoop walking or crawling, may be required for survival. In this study, a novel 3D passive vision-aided inertial system (3D PVINS) for indoor positioning was used to track the movement of 20 volunteers during an evacuation in a low visibility environment. Participants’ walking speeds using trunk flexion, trunk–knee flexion, and upright postures were measured. The investigations were carried out under emergency and non-emergency scenarios in vertical and horizontal directions, respectively. Results show that different moving directions led to a roughly 43.90% speed reduction, while posture accounted for over 17%. Gender, one of the key categories in evacuation models, accounted for less than 10% of the differences in speed. The speeds of participants under emergency scenarios when compared to non-emergency scenarios was also found to increase by 53.92–60% when moving in the horizontal direction, and by about 48.28–50% when moving in the vertical direction and descending downstairs. Our results also support the social force theory of the warming-up period, as well as the effect of panic on the facilitating occupants’ moving speed

Radioisotopes and coastal research in the Great Barrier Reef

Radioisotopes are efficient tracers of coastal processes on various spatial and temporal scales. The isotopes of radon and radium are particularly useful tools to understand hydrological land-ocean interaction because (a) activities of these isotopes are elevated in groundwater by two to three orders of magnitude in comparison with seawater, and (b) these isotopes have half-lives similar to the time scales of coastal hydrological processes such as river and groundwater discharge to the ocean, as well as coastal ocean mixing (or residence) time. The application of these isotopes to studies of land-ocean interaction in the central Great Barrier Reef region (Townsville to Cooktown) is illustrated in three recent studies: (1) coastal mapping of radon on a regional scale improves the understanding of the spatial variability of river and groundwater fluxes to the Great Barrier Reef lagoon; (2) quantification of tidal water exchange between mangrove forests and creeks demonstrates the significant contributions this process makes to water flux and associated geochemical fluxes along tropical coastlines; (3) estimates of coastal water residence time contribute to the understanding of the fate of land-derived solutes in the Great Barrier Reef Lagoon. Concurrent mapping of 222Rn (half-life 3.8 days) and salinity allows an efficient qualitative assessment of land–ocean interaction on various spatial and temporal scales. From shore-parallel transects along the Central Great Barrier Reef coastline with a surface-towed and continuously recording multi-detector system, numerous locations of elevated radon activities can be identified as terrestrially-derived submarine groundwater discharge, riverine sources, and the recirculation of seawater through crustacean burrows in mangrove forests. Variations in the inverse relationship of 222Rn and salinity in different tropical wet seasons reveal ‘timing’ aspects of large-scale freshwater input during the tropical wet season into the lagoon. Subsequently, 222Rn was used together with radium isotopes to quantify the tidal water exchange between a mangrove forest on Hinchinbrook Island and the ocean. Significant export of these radio-nuclides from the forest into a tidal creek indicates continuous tidally-driven circulation through animal burrows in the forest. The forest floor is efficiently flushed, with water flux of about 30 L m-2 day-1 of forest floor, which is equivalent to about 10% of the total burrow volume in the forest per tidal cycle. This work illustrates the physical process which supports export of organic and inorganic matter from mangrove forests to the coastal zone. Importantly, annual average circulation fluxes through mangrove forest floors are of the same order as annual river discharge in the central GBR. Finally, an improved understanding of the fate of land-derived waters is of great importance to current discussions about water quality management in the Great Barrier Reef. The mixing of coastal waters is an important parameter influencing the health of these ecosystems. Time constants associated with the decay of four naturally-occurring isotopes of radium span large time scales; 224Ra, 223Ra, 228Ra and 226Ra have half-lives of 4 days, 11 days, 6 years and 1620 years respectively. The radium quartet has been used to determine time scales of mixing of near-shore water and deep ocean water. This study demonstrates that central GBR water within 20 km of the coast is flushed with outer lagoon water on a timescale of 18–45 days, with the flushing time increasing northward. This difference likely reflects the different reef matrix density in the two zones, affecting exchange with offshore Coral Sea water

Advanced Communication Theory Techniques TECHNICAL DOCUMENTARY REPORT NO. ASD-TDR-63-186

Under this contract a number of topics have been studied and analyzed in detail in order to bring together and somewhat extend the concepts of communication theory as they apply to some current problems in digital communication systems. Radio wave channels are characterized by a model\u27 which accounts for both multiplicative and additive disturbances, A large amount of experimental data pertaining to radio disturbances is evaluated and correlated. She. importance of the Rayleigh fading channel is emphasized and previous work is extended to determine the capacity and efficiency of the Rayleigh, channel. Detection theory concepts have been extended to treat the problem of signal detection in the presence of statistically unknown additive disturbances. Several detectors based on non-parametric statistical techniques are treated in detail. Obese detectors are compared to the conventional likelihood detectors. Design procedures are formulated. Signal design techniques are used to optimize transmitted wave- forms and the improvement in system performance is determined. The criterion used in this\u27 analysis is the minimization of intersymbol influence and the minimization of transmitter power for a fixed probability of received, errors . The tradeoffs available between transmitter power and coding complexity are thoroughly investigated for the binary symmetric channel. Results are obtained for both Hamming and Bose-Chandhuri codes. Recommendations for further work in promising areas are made, the need to supplement theoretical work with experimental work is pointed ou

Charge-Transfer Excitations in the Model Superconductor HgBa2_2CuO4+δ_{\bf 4+\delta}

We report a Cu $K$-edge resonant inelastic x-ray scattering (RIXS) study of charge-transfer excitations in the 2-8 eV range in the structurally simple compound HgBa$_2$CuO$_{4+\delta}$ at optimal doping ($T_{\rm c} = 96.5$ K). The spectra exhibit a significant dependence on the incident photon energy which we carefully utilize to resolve a multiplet of weakly-dispersive ($< 0.5$ eV) electron-hole excitations, including a mode at 2 eV. The observation of this 2 eV excitation suggests the existence of a charge-transfer pseudogap deep in the superconducting phase. Quite generally, our data demonstrate the importance of exploring the incident photon energy dependence of the RIXS cross section.Comment: 5 pages, 3 figure