7,279 research outputs found

    Forest Stand Structure and Primary Production in relation to Ecosystem Development, Disturbance, and Canopy Composition

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    Temperate forests are complex ecosystems that sequester carbon (C) in biomass. C storage is related to ecosystem-scale forest structure, changing over succession, disturbance, and with community composition. We quantified ecosystem biological and physical structure in two forest chronosequences varying in disturbance intensity, and three late successional functional types to examine how multiple structural expressions relate to ecosystem C cycling. We quantified C cycling as wood net primary production (NPP), ecosystem structure as Simpson’s Index, and physical structure as leaf quantity (LAI) and arrangement (rugosity), examining how wood NPP-structure relates to light distribution and use-efficiency. Relationships between structural attributes of biodiversity, LAI, and rugosity differed. Development of rugosity was conserved regardless of disturbance and composition, suggesting optimization of vegetation arrangement over succession. LAI and rugosity showed significant positive productivity trends over succession, particularly within deciduous broadleaf forests, suggesting these measures of structure contain complementary, not redundant, information related to C cycling

    Mass transfer in a 1370 C (2500 F) lithium thermal convection loop

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    Experimental results from a test to evaluate interstitial element mass transfer effects on T-111, ASTAR 811C, and ASTAR 1211C after 5000 hours in flowing lithium at 1370 C (2500 F) are presented. No gross corrosion effects were observed. However, hafnium and nitrogen transfer to cooler regions within the loop were noted. Oxygen was in general removed from test specimens, but there was no evidence to indicate that it was a major factor in the mass transfer process. Carbon and hydrogen transfer were not detected

    Detection of Outer Rotations on 3D-Vector Fields with Iterative Geometric Correlation

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    Correlation is a common technique for the detection of shifts. Its generalization to the multidimensional geometric correlation in Clifford algebras has proven a useful tool for color image processing, because it additionally contains information about rotational misalignment. In this paper we prove that applying the geometric correlation iteratively can detect the outer rotational misalignment for arbitrary three-dimensional vector fields. Thus, it develops a foundation applicable for image registration and pattern matching. Based on the theoretical work we have developed a new algorithm and tested it on some principle examples

    Schema architecture and their relationships to transaction processing in distributed database systems

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    We discuss the different types of schema architectures which could be supported by distributed database systems, making a clear distinction between logical, physical, and federated distribution. We elaborate on the additional mapping information required in architecture based on logical distribution in order to support retrieval as well as update operations. We illustrate the problems in schema integration and data integration in multidatabase systems and discuss their impact on query processing. Finally, we discuss different issues relevant to the cooperation (or noncooperation) of local database systems in a heterogeneous multidatabase system and their relationship to the schema architecture and transaction processing

    Equine DSC Therapy of Musculoskeletal Conditions: an Ultrasonographic Evaluation

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    Musculoskeletal diseases are among the most common disorders that affect horses, and current methods to treat these disorders can be invasive and dependent on the severity of the injury. The use of mesenchymal stem cells (MSCs) may provide an effective and non-invasive method to treat equine musculoskeletal disorders. An experiment was conducted to analyze the safety of treating equine musculoskeletal disorders with an intra-articular injection of a novel stem cell product. To measure the safety of the product, the edema elicited by the injection of the product was measured using ultrasonographic images. These images were taken before the injection and seven and fourteen days after the injection. To measure edema at the three time points, three soft tissue measurements were taken for horses affected by tendonitis/desmitis and four measurements were taken for horses affected by osteoarthritis at each time point. Edema that the intra-articular injection of the stem cells may have elicited was resolved and no longer statistically significant within the first week after injection. The transient edema observed suggests that the intra-articular injection of the stem cell product is a safe option for treating equine musculoskeletal disorders.No embargoAcademic Major: Zoolog

    A General Geometric Fourier Transform Convolution Theorem

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    The large variety of Fourier transforms in geometric algebras inspired the straight forward definition of ``A General Geometric Fourier Transform`` in Bujack et al., Proc. of ICCA9, covering most versions in the literature. We showed which constraints are additionally necessary to obtain certain features like linearity, a scaling, or a shift theorem. In this paper we extend the former results by a convolution theorem

    Convolution products for hypercomplex Fourier transforms

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    Hypercomplex Fourier transforms are increasingly used in signal processing for the analysis of higher-dimensional signals such as color images. A main stumbling block for further applications, in particular concerning filter design in the Fourier domain, is the lack of a proper convolution theorem. The present paper develops and studies two conceptually new ways to define convolution products for such transforms. As a by-product, convolution theorems are obtained that will enable the development and fast implementation of new filters for quaternionic signals and systems, as well as for their higher dimensional counterparts.Comment: 18 pages, two columns, accepted in J. Math. Imaging Visio

    Utilizing Ground-Based LIDAR Measurements to Aid Autonomous Airdrop Systems

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    Uncertainty in atmospheric winds represents one of the primary sources of landing error in airdrop systems. In this work, a ground-based LIDAR system samples the wind field at discrete points above the target and transmits real-time data to approaching autonomous airdrop systems. In simulation and experimentation, the inclusion of a light detection and ranging (LIDAR) system showed a maximum of 40% improvement over unaided autonomous airdrop systems. Wind information nearest ground level has the largest impact on improving accuracy
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