Object recognition using shape-from-shading

This paper investigates whether surface topography information extracted from intensity images using a recently reported shape-from-shading (SFS) algorithm can be used for the purposes of 3D object recognition. We consider how curvature and shape-index information delivered by this algorithm can be used to recognize objects based on their surface topography. We explore two contrasting object recognition strategies. The first of these is based on a low-level attribute summary and uses histograms of curvature and orientation measurements. The second approach is based on the structural arrangement of constant shape-index maximal patches and their associated region attributes. We show that region curvedness and a string ordering of the regions according to size provides recognition accuracy of about 96 percent. By polling various recognition schemes. including a graph matching method. we show that a recognition rate of 98-99 percent is achievable

New constraints on data-closeness and needle map consistency for shape-from-shading

This paper makes two contributions to the problem of needle-map recovery using shape-from-shading. First, we provide a geometric update procedure which allows the image irradiance equation to be satisfied as a hard constraint. This not only improves the data closeness of the recovered needle-map, but also removes the necessity for extensive parameter tuning. Second, we exploit the improved ease of control of the new shape-from-shading process to investigate various types of needle-map consistency constraint. The first set of constraints are based on needle-map smoothness. The second avenue of investigation is to use curvature information to impose topographic constraints. Third, we explore ways in which the needle-map is recovered so as to be consistent with the image gradient field. In each case we explore a variety of robust error measures and consistency weighting schemes that can be used to impose the desired constraints on the recovered needle-map. We provide an experimental assessment of the new shape-from-shading framework on both real world images and synthetic images with known ground truth surface normals. The main conclusion drawn from our analysis is that the data-closeness constraint improves the efficiency of shape-from-shading and that both the topographic and gradient consistency constraints improve the fidelity of the recovered needle-map

Recovering facial shape using a statistical model of surface normal direction

In this paper, we show how a statistical model of facial shape can be embedded within a shape-from-shading algorithm. We describe how facial shape can be captured using a statistical model of variations in surface normal direction. To construct this model, we make use of the azimuthal equidistant projection to map the distribution of surface normals from the polar representation on a unit sphere to Cartesian points on a local tangent plane. The distribution of surface normal directions is captured using the covariance matrix for the projected point positions. The eigenvectors of the covariance matrix define the modes of shape-variation in the fields of transformed surface normals. We show how this model can be trained using surface normal data acquired from range images and how to fit the model to intensity images of faces using constraints on the surface normal direction provided by Lambert's law. We demonstrate that the combination of a global statistical constraint and local irradiance constraint yields an efficient and accurate approach to facial shape recovery and is capable of recovering fine local surface details. We assess the accuracy of the technique on a variety of images with ground truth and real-world images

Inversion algorithms for the microwave remote sensing of soil moisture. Experiments with swept frequency microwaves

Two experiments were performed employing swept frequency microwaves for the purpose of investigating the reflectivity from soil volumes containing both discontinuous and continuous changes in subsurface soil moisture content. Discontinuous moisture profiles were artificially created in the laboratory while continuous moisture profiles were induced into the soil of test plots by the environment of an agricultural field. The reflectivity for both the laboratory and field experiments was measured using bi-static reflectometers operated over the frequency ranges of 1.0 to 2.0 GHz and 4.0 to 8.0 GHz. Reflectivity models that considered the discontinuous and continuous moisture profiles within the soil volume were developed and compared with the results of the experiments. This comparison shows good agreement between the smooth surface models and the measurements. In particular the comparison of the smooth surface multi-layer model for continuous moisture profiles and the yield experiment measurements points out the sensitivity of the specular component of the scattered electromagnetic energy to the movement of moisture in the soil

X-ray time lags in AGN: inverse-Compton scattering and spherical corona model

We develop a physically motivated, spherical corona model to investigate the frequency-dependent time lags in AGN. The model includes the effects of Compton up-scattering between the disc UV photons and coronal electrons, and the subsequent X-ray reverberation from the disc. The time lags are associated with the time required for multiple scatterings to boost UV photons up to soft and hard X-ray energies, and the light crossing time the photons take to reach the observer. This model can reproduce not only low-frequency hard and high-frequency soft lags, but also the clear bumps and wiggles in reverberation profiles which should explain the wavy-residuals currently observed in some AGN. Our model supports an anti-correlation between the optical depth and coronal temperatures. In case of an optically thin corona, time delays due to propagating fluctuations may be required to reproduce observed time lags. We fit the model to the lag-frequency data of 1H0707-495, Ark 564, NGC 4051 and IRAS 13224-3809 estimated using the minimal bias technique so that the observed lags here are highest-possible quality. We find their corona size is ~7-15 r_g having the constrained optical depth ~2-10. The coronal temperature is ~150-300 keV. Finally, we note that the reverberation wiggles may be signatures of repeating scatters inside the corona that control the distribution of X-ray sources.Comment: 15 pages, 10 figures, accepted for publication in MNRA

Droplet evaporation losses during sprinkler irrigation: an overview

A detailed understanding regarding the evaporation losses in sprinkler irrigation is important for developing as well as adopting appropriate water conservation strategies. To explain this phenomenon many theoretical and experimental studies have been conducted since the 1950‟s. Notwithstanding all these efforts, the contribution of droplet evaporation to the total evaporation losses during sprinkler irrigation is still a controversial issue in the irrigation community. There is a substantial difference among researchers regarding the magnitudes of the different components of the total evaporation in sprinkler irrigation especially droplet evaporation losses. Field studies reported that the droplet evaporation losses ranged from 2 – 45%, whereas theoretical studies indicated that it is less than 1%. This is due largely to the limitations of the traditional measurement methods. However, it is likely that these limitations can be overcome and accurate measurements obtained using the eddy covariance (ECV) technique

An Analysis of Kinetic Response Variability

Studies evaluating variability of force as a function of absolute force generated are synthesized. Inconsistencies in reported estimates of this relationship are viewed as a function of experimental constraints imposed. Typically, within-subject force variability increases at a negative accelerating rate with equal increments in force produced. Current pulse-step and impulse variability models are unable to accommodate this description, although the notion of efficiency is suggested as a useful construct to explain the description outlined

Cruise aerodynamics of USB nacelle/wing geometric variations

Experimental results are presented on aerodynamic effects of geometric variations in upper surface blown nacelle configurations at high speed cruise conditions. Test data include both force and pressure measurements on two and three dimensional models powered by upper surface blowing nacelles of varying geometries. Experimental results are provided on variations in nozzle aspect ratio, nozzle boattail angle, and multiple nacelle installations. The nacelles are ranked according to aerodynamic drag penalties as well as overall installed drag penalties. Sample effects and correlations are shown for data obtained with the pressure model

Towards adaptive operational requirements for optimal application of evaporation-suppressing monolayer to reservoirs via a 'universal design framework'

Much of the chemical monolayer-based evaporation mitigation research was generated in the 1950s, 60s and 70s centred on the use of spreading long-chain fatty alcohols, such as hexadecanol (C16) and octadecanol (C18), on the water surface. Many researchers from this era have reported highly variable performance results (anywhere from 0-30% efficiency) attributing the highly variable evaporation reduction achieved to film volatilisation, drift, beaching on the lee shore and waves which can break-up or submerge the film.Failure to address this requirement has undoubtedly contributed to the lack of development in the use of monolayers despite some demonstration of useful evaporation suppression performance. In addition recent studies have also indicated that all water bodies have a naturally-occurring surface film, referred to as a microlayer, which can interact with artificial (chemical) monolayers. Natural microlayers are produced by hydrophobic plant waxes, phenolic compounds and other humified material, which concentrates populations of micro-organisms capable of utilizing these materials as organic substrates. This explains why common artificial monolayers (with carbon chain lengths of up to 16) are highly susceptible to biodegradation. Studies on Australian brown water storages reveal highly concentrated microbial microlayer communities, due to the coincidence of leaf and bark fall with low rainfall (Pittaway and van den Ancker 2009). This variation in the concentration of humified organic compounds in the storages is associated with both the volume of the storage, and the riparian vegetation within the water catchment. This paper sets out a strategic approach to the use of monolayer on a reservoir for evaporation mitigation. The approach recognises that every reservoir will have a specific set of user and environmental considerations which leads to a unique set of operational requirements. In order to capture and utilise this information a Universal Design Framework (UDF) has been developed. The UDF serves two purposes, firstly to inform the selection of monolayer material and system design for any given site (‘Planning Mode’), and secondly to inform (and potentially autonomously manage) day-to-day operations, i.e. the timing and amounts of monolayer application (‘Operational Mode’). The UDF takes into account the following parameters: • Critical water requirement periods: These will vary from location to location and at different times of the year. Hence, this is a user determined input. • Economics: The dollars-per-megalitre value of water will also vary from location to location and at different time of the year with respect to critical water requirement periods (e.g. irrigated cropping close to harvest). Included in this input is a user defined annual maximum cost outlay for the monolayer-based system. • Water storage factors: Inputs differ slightly depending on storage type (i.e. ring tank versus gully dam), but generally require information of length, width, shape, bank height, freeboard, full supply volume and geographical co-ordinate points for storage orientation. This would be determined by a basic on-site analysis • Climate and weather factors: Monthly average evaporation demand, rainfall and ambient air temperature information is required, including particularly wind speed frequency and prevailing wind direction, (e.g. from a local Automatic Weather Station (AWS) or via the Bureau of Meteorology SILO database, http://www.longpaddock.qld.gov.au/silo/). In the Planning Mode mean and extreme historical climate data are used; and in the Operational Mode prevailing conditions are required. • Water quality and biological factors: Assessments are made of water source/s (e.g. runoff versus bore), water colour, turbidity, water chemistry (pH, electrical conductivity and UV absorbency), plus density of local catchment vegetation and catchment area. Once the above parameters are known, the UDF is used to determine (in Planning Mode) the most suitable monolayer material/s and optimal arrangement of application equipment, including number of applicators, their arrangement and application strategies for the particular reservoir and monolayer product. In Operational Mode the UDF will guide (or if required, fully control) operational procedures, i.e. the implementation of a unique application strategy for a specific product according to the hour-by-hour prevailing conditions. This paper also outlines decision-making processes within the UDF. Firstly, to determine suitable monolayer materials the UDF compares water quality and biological characteristics of the particular site to those of six benchmark reservoirs in SE Queensland which have been studied in detail (Pittaway and van den Ancker 2009). The biologically-closest informs the choice of appropriate monolayer material/s. Once the selection of a monolayer is made there are a number of unique characteristics that material possesses that will substantially influence the application strategies. Secondly, a simulation platform has been developed to determine the application strategies and operational requirements for the reservoir. The simulation enables rapid evaluation of a range of different sample water bodies to populate a decision chart similar to that for monolayer material selection. A central component of the simulation platform is a fluid-mechanical model of the dispersal of monolayer across a water surface area under the influence of environmental variables, principally wind speed and wind direction, which (in Planning Mode) determines: • optimal spacing between application points, • amount of monolayer applied from each applicator as well as the total amount applied, • placement of applicators to achieve optimal surface coverage, • number of applicator types required, and • percentage of surface coverage under a range of wind speeds and directions. The above simulated output information is unique to the particular reservoir and is essentially a specification for the design and operation of a monolayer application system for that specific site, and is used firstly (Planning Mode) to select appropriate application equipment capable of satisfying the monolayer application requirements; and secondly, if installed as planned, as the basis for day-to-day monolayer application (Operational Mode). Simulation results to date indicate that from large reservoirs, optimal surface coverage is best achieved by a number of fixed application points surrounding and within the reservoir spaced no further than 12 metres apart; and that a greater concentration of applicators is required upwind from the prevailing wind direction in addition to higher rates of monolayer application