9,070 research outputs found

    Annual Report Readership: A Study of an Agricultural Supply Cooperative

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    Recent corporate collapses have focussed attention on the (un)reliability of financial information. However, although the agricultural sector, which is significant globally, is run primarily using the cooperative form, there is scant research on these users' perception of financial information. Therefore this paper examines members' readership and understanding of the annual reports of a large, fertiliser cooperative. The findings show that there is a lack of readership of the annual report, due to a lack of understanding and a lack of time. A minority of non-readers trust directors to "do a good job". Preparers of information should focus on making reports more user-friendly and evidence suggests that financial information could be released more strategically using other sources of communication, namely other print media and the internet.cooperatives, annual reports, readership, understanding, Agribusiness,

    The Role of Subsurface Flows in Solar Surface Convection: Modeling the Spectrum of Supergranular and Larger Scale Flows

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    We model the solar horizontal velocity power spectrum at scales larger than granulation using a two-component approximation to the mass continuity equation. The model takes four times the density scale height as the integral (driving) scale of the vertical motions at each depth. Scales larger than this decay with height from the deeper layers. Those smaller are assumed to follow a Kolomogorov turbulent cascade, with the total power in the vertical convective motions matching that required to transport the solar luminosity in a mixing length formulation. These model components are validated using large scale radiative hydrodynamic simulations. We reach two primary conclusions: 1. The model predicts significantly more power at low wavenumbers than is observed in the solar photospheric horizontal velocity spectrum. 2. Ionization plays a minor role in shaping the observed solar velocity spectrum by reducing convective amplitudes in the regions of partial helium ionization. The excess low wavenumber power is also seen in the fully nonlinear three-dimensional radiative hydrodynamic simulations employing a realistic equation of state. This adds to other recent evidence suggesting that the amplitudes of large scale convective motions in the Sun are significantly lower than expected. Employing the same feature tracking algorithm used with observational data on the simulation output, we show that the observed low wavenumber power can be reproduced in hydrodynamic models if the amplitudes of large scale modes in the deep layers are artificially reduced. Since the large scale modes have reduced amplitudes, modes on the scale of supergranulation and smaller remain important to convective heat flux even in the deep layers, suggesting that small scale convective correlations are maintained through the bulk of the solar convection zone.Comment: 36 pages, 6 figure

    Option pricing in affine generalized Merton models

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    In this article we consider affine generalizations of the Merton jump diffusion model [Merton, J. Fin. Econ., 1976] and the respective pricing of European options. On the one hand, the Brownian motion part in the Merton model may be generalized to a log-Heston model, and on the other hand, the jump part may be generalized to an affine process with possibly state dependent jumps. While the characteristic function of the log-Heston component is known in closed form, the characteristic function of the second component may be unknown explicitly. For the latter component we propose an approximation procedure based on the method introduced in [Belomestny et al., J. Func. Anal., 2009]. We conclude with some numerical examples

    A probabilistic framework for forward model-driven SHM

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    A challenge for many structural health monitoring (SHM) technologies is the lack of available damage state data. This problem arises due to cost implications of damaging a structure in addition to issues associated with the feasibility and safety of testing a structure in multiple damage scenarios. Many data-driven approaches to SHM are successful when the appropriate damage state data is available, however the problem of obtaining data for various damage states of interest restricts their use in industry. Forward model-driven approaches to SHM seek to aid this challenge. This methodology uses validated physical models to generate predictions of the system at different damage states, providing machine learning strategies with training data, to infer decision bounds. An ideal forward model-driven SHM framework is one in which one or more physical models are able to produce predictions that are statistically representative of data obtained from the physical structure. Validation of these physical models requires observational data. As a result, validation is performed on a component or sub-system level where damage state data can be more easily obtained. This methodology requires the combination of several low-level physical models via a multi-level uncertainty integration technique. This paper outlines such a framework using uncertainty quantification technologies and statistical methods for combining low-level probabilistic models whilst accounting of discrepancies that may occur in interactions with other low-level models. The method contains several statistical techniques for accounting for model discrepancies that may occur at any point throughout the modelling process. Model discrepancies arise due to missing physics or simplifications and result in the model deviating from the observed physics even when the ‘true’ parameters of the model are known. By accounting for model discrepancies throughout the framework the approach allows for further insight into model form errors whilst also improving the techniques ability to produce statistically representative predictions across damage states. The paper presents the key stages highlighting the relevant technologies and application considerations. Additionally, a discussion of integration with current data-driven approaches and the appropriate machine learning tools is given for a forward model-driven SHM approach

    Effectiveness of the ADEC as a level 2 screening test for young children with suspected autism spectrum disorders in a clinical setting

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    Background The Autism Detection in Early Childhood (ADEC) is a clinician-administered, Level 2 screening tool. A retrospective file audit was used to investigate its clinical effectiveness. Method Toddlers referred to an Australian child development service between 2008 and 2010 (N?=?53, M age?=?32.2 months) were screened with the ADEC. Their medical records were reviewed in 2013 when their mean age was 74.5 months, and the original ADEC screening results were compared with later diagnostic outcomes. Results The ADEC had good sensitivity (87.5%) and moderate specificity (62%). Three behaviours predicted autism spectrum disorders (ASDs): response to name, gaze switching, and gaze monitoring (p???.001). Conclusions The ADEC shows promise as a screening tool that can discriminate between young children with ASDs and those who have specific communication disorders or developmental delays that persist into middle childhood but who do not meet the criteria for ASDs

    Orbital assembly and maintenance study. Executive summary

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    A sound, practical approach for the assembly and maintenance of very large structures in space is presented. The methods and approaches for assembling two large structures are examined. The maintenance objectives include the investigation of methods to maintain five geosynchronous satellites. The two assembly examples are a 200-meter-diameter radio astronomy telescope and a 1,000-meter-diameter microwave power transmission system. The radio astronomy telescope operates at an 8,000-mile altitude and receives RF signals from space. The microwave power transmission system is part of a solar power satellite that will be used to transmit converted solar energy to microwave ground receivers. Illustrations are included

    Sun-angle effects on the red and near infrared reflectances of five different crop canopies

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    The objective of this paper is to study relationships between dai/y variations in sun angles and red and near infrared reflectances measured throughout a growing season over different types of crop canopies. Five architecturally different crop canopies were planted: wheat (NNW-SSE rows 0.18 m and 0.35 m apart), barley (NNW-SSE rows 0.18 m apart), corn (NNWSSE rows 0.46 m apart), and sunflower (N-S rows 0.92 m apart). Each canopy was planted at three different densifies in order to add intraspecies variability. Spectral reflectances were measured with a sensor in the nadir position located on a ground platform. Changes in sun angles usually affected the red more than near infrared reflectances. Within each crop, the canopies with the lowest LAI a/ways showed the larges! variations in spectral reflectances. But among the crops, the importance of changing sun angles on crop canopy reflectances varied with the architecture of the canopy. Red reflectances collected over corn and sunflower at LAI of 6 were insensitive to changes in sun angles, while those collected above sunflower showed significant differences when LAI was around 4. The higher proportion of horizontal foliar area compared to the vertical one in corn canopies could account for this difference between the two crops, since a canopy with horizontal foliar distribution is a nearer approximation of a lambertian surface. The differences in row width and orientation could also explain some of these differences. Reflectances of wheat canopies planted with rows 0.35 m apart showed larger red reflectance variations within a day than those planted 0.17 m apart. The maximum red reflectances always appeared when the sun was in fine with row direction. The fact that most rapid variations in red reflectances were occurring around this particular time of the day also confirmed that there is a strong interaction between row direction and width with the position of the sun in the sky. The magnitude of the effect of the variations of sun angles on crop canopy spectral reflectances was shown to be dependent on the species, planting patterns, wavelength band, and sky conditions. Le présent article décrit une étude des relations entre les variations quotidiennes de l'angle du soleil ainsi que des réflectances dans le rouge et le proche infrarouge mesurées tout au long d'une saison de récolte sur différents types de couverts végétaux. Cinq couverts végétaux de structure différente ont été semés: blé (rangs NNO-SSE à intervalles de 0,18 et 0,35 mÚtres), orge (rangs NNO-SSE à intervalles de 0,18 mÚtre), maïs (rangs NNO-SSE à intervalles de 0,46 mÚtre) et tournesol (rangs N-S à intervalles de 0,92 mÚtre). Chaque couvert végétal a été semé à trois densités différentes de maniÚre à pouvoir mesurer la variabilité au sein de chaque espÚce. Les réflectances spectrales ont été mesurées à la position nadir à l'aide d'un capteur fixé à une plate-forme au sol. En général, les variations de l'angle du soleil touchaient davantage les réflectances dans le rouge que les réflectances dans le proche infrarouge. Pour chaque culture, les couverts ayant l'indice de surface foliaire (ISF) le moins élevé ont systématiquement donné la plus grande variation au niveau des réflectances spectrales. Par contre, entre les diverses cultures, la variation de l'angle du soleil sur les réflectances des couverts végétaux était fonction de la structure du couvert. Les réflectances rouges recueillies au-dessus du maïs et du tournesol avec un ISF de 6 étaient insensibles aux variations de l'angle du soleil, tandis que celles mesurées au-dessus des tournesols variaient substantiellement lorsque l'ISF était aux environs de 4. Cette différence entre les deux cultures peut s'expliquer par la présence d'une plus grande distribution foliaire horizontale comparativement à la surface verticale offerte par le couvert de maïs, puisqu'un couvert ayant une distribution foliaire horizontale se rapproche davantage d'une surface lambertienne. La différence dans la largeur et l'orientation des rangs pourrait aussi expliquer certaines de ces différences. Les couverts de blé semés en rangs à intervalles de 0,35 mÚtre ont donné des variations de réflectances dans le rouge plus grandes dans une journée que ceux semés à intervalles de 0,17 mÚtre. Les réflectances maximales dans le rouge se produisaient toujours lorsque le soleil était en ligne avec les rangs. Le fait que la plupart des variations rapides des réflectances dans le rouge se produisaient à ce moment particulier de la journée a aussi confirmé qu'il existe une forte corrélation entre la direction et la largeur des rangs et la position du soleil dans le ciel. Cette étude a démontré que l'ampleur de l'incidence des variations de l'angle du soleil sur les réflectances spectrales des couverts végétaux est fonction de l'espÚce, du mode de semence, de la longueur d'ondes de la bande et des conditions du ciel

    Influence of wind on crop canopy reflectance measurements

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    Remote sensing techniques of measuring red and far-red crop canopy reflectance are frequently used to estimate crop canopy characteristics. The variability introduced in reflectance data from nonvegetative factors such as wind decreases the usefulness of the techniques. The objective of this study was to quantify and minimize the variability from wind on spectral reflectances. Red and far-red reflectances were acquired above wheat, barley, and alfalfa canopies throughout days of changing wind conditions. Periods of 312 s with little changes in irradiance values were used for the analysis. Wind had negligible effect on reflectances of a short canopy such as cut alfalfa, while it had a significant effect on reflectances from canopies with a higher vertical structure, particularly during gusty conditions. Within the windy and calm periods, extreme values of spectral reflectance differed by 60% and 12%, respectively, in the red, and by 40% and 8% in the far-red for the barley canopy. For the compact and dense canopy structure of alfalfa, these differences reached a maximum of 10% under windy conditions in both spectral regions. The plant canopy architecture, the wind conditions, and the spectral regions all affected the magnitude of the influence of wind on crop canopy spectral reflectances. The mean reflectance of a canopy overestimated the true reflectance by 2–4% while the use of the median reduced this overestimation. Sampling requirements for this sensor are evaluated, and the possibility of decreasing either the sampling rate or the sampling period is discussed

    Nitrogen hydrides in interstellar gas: Herschel/HIFI observations towards G10.6-0.4 (W31C)

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    The HIFI instrument on board the Herschel Space Observatory has been used to observe interstellar nitrogen hydrides along the sight-line towards G10.6−0.4 in order to improve our understanding of the interstellar chemistry of nitrogen. We report observations of absorption in NH N = 1 ← 0, J = 2 ← 1 and ortho-NH_2 1_(1,1) ← 0_(0,0). We also observed ortho-NH_3 1_0 ← 0_0, and 2_0 ← 1_0, para-NH_3 2_1 ← 1_1, and searched unsuccessfully for NH^+. All detections show emission and absorption associated directly with the hot-core source itself as well as absorption by foreground material over a wide range of velocities. All spectra show similar, non-saturated, absorption features, which we attribute to diffuse molecular gas. Total column densities over the velocity range 11−54 km s^(−1) are estimated. The similar profiles suggest fairly uniform abundances relative to hydrogen, approximately 6 × 10^(−9), 3 × 10^(−9), and 3 × 10^(−9) for NH, NH_2, and NH_3, respectively. These abundances are discussed with reference to models of gas-phase and surface chemistry

    Convection cells induced by spontaneous symmetry breaking

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    Ubiquitous in nature, convection cells are a clear signature of systems out-of-equilibrium. Typically, they are driven by external forces, like gravity (in combination with temperature gradients) or shear. In this article, we show the existence of such cells in possibly the simplest system, one that involves only a temperature gradient. In particular, we consider an Ising lattice gas on a square lattice, in contact with two thermal reservoirs, one at infinite temperature and another at TT. When this system settles into a non-equilibrium stationary state, many interesting phenomena exist. One of these is the emergence of convection cells, driven by spontaneous symmetry breaking when TT is set below the critical temperature.Comment: published version, 2 figures, 5 page
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