The Experts below are selected from a list of 3090 Experts worldwide ranked by ideXlab platform

Cardona Cesar - One of the best experts on this subject based on the ideXlab platform.

  • Earth microbial co-occurrence network reveals Interconnection Pattern across microbiomes.
    eScholarship University of California, 2020
    Co-Authors: Ma Bin, Wang Yiling, Ye Shudi, Liu Shan, Stirling Erinne, Gilbert, Jack A, Faust Karoline, Knight Rob, Jansson, Janet K, Cardona Cesar
    Abstract:

    BACKGROUND:Microbial interactions shape the structure and function of microbial communities; microbial co-occurrence networks in specific environments have been widely developed to explore these complex systems, but their Interconnection Pattern across microbiomes in various environments at the global scale remains unexplored. Here, we have inferred an Earth microbial co-occurrence network from a communal catalog with 23,595 samples and 12,646 exact sequence variants from 14 environments in the Earth Microbiome Project dataset. RESULTS:This non-random scale-free Earth microbial co-occurrence network consisted of 8 taxonomy distinct modules linked with different environments, which featured environment specific microbial co-occurrence relationships. Different topological features of subnetworks inferred from datasets trimmed into uniform size indicate distinct co-occurrence Patterns in the microbiomes of various environments. The high number of specialist edges highlights that environmental specific co-occurrence relationships are essential features across microbiomes. The microbiomes of various environments were clustered into two groups, which were mainly bridged by the microbiomes of plant and animal surface. Acidobacteria Gp2 and Nisaea were identified as hubs in most of subnetworks. Negative edges proportions ranged from 1.9% in the soil subnetwork to 48.9% the non-saline surface subnetwork, suggesting various environments experience distinct intensities of competition or niche differentiation. Video abstract CONCLUSION: This investigation highlights the Interconnection Patterns across microbiomes in various environments and emphasizes the importance of understanding co-occurrence feature of microbiomes from a network perspective

  • Earth microbial co-occurrence network reveals Interconnection Pattern across microbiomes
    'Springer Science and Business Media LLC', 2020
    Co-Authors: Ma Bin, Wang Yiling, Ye Shudi, Liu Shan, Stirling Erinne, Gilbert, Jack A, Faust Karoline, Knight Rob, Jansson, Janet K, Cardona Cesar
    Abstract:

    BACKGROUND: Microbial interactions shape the structure and function of microbial communities; microbial co-occurrence networks in specific environments have been widely developed to explore these complex systems, but their Interconnection Pattern across microbiomes in various environments at the global scale remains unexplored. Here, we have inferred an Earth microbial co-occurrence network from a communal catalog with 23,595 samples and 12,646 exact sequence variants from 14 environments in the Earth Microbiome Project dataset. RESULTS: This non-random scale-free Earth microbial co-occurrence network consisted of 8 taxonomy distinct modules linked with different environments, which featured environment specific microbial co-occurrence relationships. Different topological features of subnetworks inferred from datasets trimmed into uniform size indicate distinct co-occurrence Patterns in the microbiomes of various environments. The high number of specialist edges highlights that environmental specific co-occurrence relationships are essential features across microbiomes. The microbiomes of various environments were clustered into two groups, which were mainly bridged by the microbiomes of plant and animal surface. Acidobacteria Gp2 and Nisaea were identified as hubs in most of subnetworks. Negative edges proportions ranged from 1.9% in the soil subnetwork to 48.9% the non-saline surface subnetwork, suggesting various environments experience distinct intensities of competition or niche differentiation. Video abstract CONCLUSION: This investigation highlights the Interconnection Patterns across microbiomes in various environments and emphasizes the importance of understanding co-occurrence feature of microbiomes from a network perspective.status: publishe

Marco Forzati - One of the best experts on this subject based on the ideXlab platform.

  • Scalable Passive Optical Network Architecture for Reliable Service Delivery
    Journal of Optical Communications and Networking, 2011
    Co-Authors: Jing Chen, Mohsan Niaz Chughtai, Lena Wosinska, Marco Forzati
    Abstract:

    A scalable and reliable architecture for both a wavelength division multiplexing passive optical network and a hybrid wavelength and time division multiplexing passive optical network with self-healing capability is presented and evaluated. Our protection scheme is compatible with a cascaded arrayed waveguide grating that can accommodate an ultra-large number of end users. A simple Interconnection Pattern between two adjacent optical network units (ONUs) is applied in order to provide protection for distributed fibers between a remote node and the ONUs. Therefore, the investment cost on a per-user basis can be significantly reduced. Meanwhile, the performance evaluation shows that our approach can achieve high connection availability while maintaining the support of long reach and high splitting ratio.

P Van Mieghem - One of the best experts on this subject based on the ideXlab platform.

  • interconnectivity structure of a general interdependent network
    Physical Review E, 2016
    Co-Authors: P Van Mieghem
    Abstract:

    A general two-layer network consists of two networks G_{1} and G_{2}, whose Interconnection Pattern is specified by the interconnectivity matrix B. We deduce desirable properties of B from a dynamic process point of view. Many dynamic processes are described by the Laplacian matrix Q. A regular topological structure of the interconnectivity matrix B (constant row and column sum) enables the computation of a nontrivial eigenmode (eigenvector and eigenvalue) of Q. The latter eigenmode is independent from G_{1} and G_{2}. Such a regularity in B, associated to equitable partitions, suggests design rules for the construction of interconnected networks and is deemed crucial for the interconnected network to show intriguing behavior, as discovered earlier for the special case where B=wI refers to an individual node to node Interconnection with Interconnection strength w. Extensions to a general m-layer network are also discussed.

R A Novotny - One of the best experts on this subject based on the ideXlab platform.

  • six stage digital free space optical switching network using symmetric self electro optic effect devices
    Applied Optics, 1993
    Co-Authors: F B Mccormick, T J Cloonan, F A P Tooley, Anthony L Lentine, Jose M Sasian, J L Brubaker, Rick L Morrison, Sonya L Walker, Randall J Crisci, R A Novotny
    Abstract:

    We describe the design and demonstration of an extended generalized shuffle Interconnection network, centrally controlled by a personal computer. A banyan Interconnection Pattern is implemented by use of computer-generated Fourier holograms and custom metallization at each 32 × 32 switching node array. Each array of electrically controlled tristate symmetric self-electro-optic-effect devices has 10,240 optical pinouts and 32 electrical pinouts, and the six-stage system occupies a 9 in. × 12.5 in. (22.9 cm × 31.7 cm) area. Details of the architecture, optical and mechanical design, and system alignment and tolerancing are presented.

  • six stage digital free space optical switching network using symmetric self electro optic effect devices
    Applied Optics, 1993
    Co-Authors: F B Mccormick, T J Cloonan, F A P Tooley, Anthony L Lentine, Jose M Sasian, J L Brubaker, Rick L Morrison, Sonya L Walker, Randall J Crisci, R A Novotny
    Abstract:

    We describe the design and demonstration of an extended generalized shuffle Interconnection network, centrally controlled by a personal computer. A banyan Interconnection Pattern is implemented by use of computer-generated Fourier holograms and custom metallization at each 32 × 32 switching node array. Each array of electrically controlled tristate symmetric self-electro-optic-effect devices has 10,240 optical pinouts and 32 electrical pinouts, and the six-stage system occupies a 9 in. × 12.5 in. (22.9 cm × 31.7 cm) area. Details of the architecture, optical and mechanical design, and system alignment and tolerancing are presented.

Doelman R. - One of the best experts on this subject based on the ideXlab platform.

  • Rank-based optimization techniques for estimation problems in optics
    2019
    Co-Authors: Doelman R.
    Abstract:

    Aberrations in optical systems, such as telescopes and microscopes, degrade the quality of the images that can be produced by these systems. For example, an object that is positioned out of focus produces a blurred image on a camera sensor and the turbulent air in the earth’s atmosphere reduces the imaging performance of telescopes. In this thesis we only consider wavefront aberrations. AO can be used to compensate for these wavefront aberrations. The working principle of AO is to quantify by measuring or estimation the wavefront aberration and to dynamically adjust wavefront modulating devices, such as Deformable Mirrors (DMs), to counteract the aberration and thereby improving the optical performance. The estimation of the wavefront aberration based on images of a point source is called phase retrieval, which is a highly nonlinear estimation problem. The success of the estimation usually depends on the (type of) algorithm, the available information on the aberration that is incorporated in the estimate, and the degree to which the model of the optical system corresponds to reality. In this thesis we propose a convex optimization-based method for phase retrieval. The method allows for easy inclusion of many types of prior information on the aberration. Furthermore, we develop an efficient implementation of the optimization. The robustness of the approach against measurement noise is investigated and compared with several other state of the art algorithms. Experimental validation shows the algorithmis well able to estimate aberrations in real-life circumstances. A new type of prior information is introduced to estimate dynamic wavefront aberrations. In literature and in practice, the optical path is split between either a wavefront sensor and a camera, or between multiple cameras in order to reliable estimate an aberration. The inherent problem is that between the sensor and cameras the aberration can differ (Non-Common Path (NCP) errors), and a wrong estimate is used in the compensation by the AO system. We propose a method to estimate the aberration from measurements by a single camera, by assuming that the aberration evolves according to (non-specific) model, i.e. the dynamics are contained in a model-set. At the same time that we estimate the aberration, we also identify the dynamics according to which the aberration evolves over time. The estimation of the wavefront aberration based on images of an unknown object is called blind deconvolution if both the aberration and object are estimated. Like phase retrieval, this too is a highly nonlinear estimation problem. We propose the first convexoptimization based estimation method for blind deconvolution problems that estimate aberration and object when the images are acquired using coherent illumination. The method allows for the inclusion of many existing types of prior information on the object and/or aberration. Finally, we analyze controllers for segmented mirrors in large ground-based telescopes. These mirrors consist of many interconnected hexagonal segments. This distributed nature of the system warrants the investigation into whether the controller that keeps the segments aligned can be designed in such a way that it can be distributed over the segments as well, essentially resulting in a distributed controller where local controllers communicate with each other. What complicates the analysis is that the dynamics across segments are not necessarily decoupled: the wind load can be correlated and the flexibility in the supporting structure of the segments can cause dynamic coupling. We investigate the design of a distributed controller that incorporates these global dynamics. Furthermore, we investigate the performance of the distributed controller and howit relates to the communication and Interconnection Pattern of the local controllers.Numerics for Control & Identificatio

  • Rank-based optimization techniques for estimation problems in optics
    2019
    Co-Authors: Doelman R.
    Abstract:

    Aberrations in optical systems, such as telescopes and microscopes, degrade the quality of the images that can be produced by these systems. For example, an object that is positioned out of focus produces a blurred image on a camera sensor and the turbulent air in the earth’s atmosphere reduces the imaging performance of telescopes. In this thesis we only consider wavefront aberrations. AO can be used to compensate for these wavefront aberrations. The working principle of AO is to quantify by measuring or estimation the wavefront aberration and to dynamically adjust wavefront modulating devices, such as Deformable Mirrors (DMs), to counteract the aberration and thereby improving the optical performance. The estimation of the wavefront aberration based on images of a point source is called phase retrieval, which is a highly nonlinear estimation problem. The success of the estimation usually depends on the (type of) algorithm, the available information on the aberration that is incorporated in the estimate, and the degree to which the model of the optical system corresponds to reality. In this thesis we propose a convex optimization-based method for phase retrieval. The method allows for easy inclusion of many types of prior information on the aberration. Furthermore, we develop an efficient implementation of the optimization. The robustness of the approach against measurement noise is investigated and compared with several other state of the art algorithms. Experimental validation shows the algorithmis well able to estimate aberrations in real-life circumstances. A new type of prior information is introduced to estimate dynamic wavefront aberrations. In literature and in practice, the optical path is split between either a wavefront sensor and a camera, or between multiple cameras in order to reliable estimate an aberration. The inherent problem is that between the sensor and cameras the aberration can differ (Non-Common Path (NCP) errors), and a wrong estimate is used in the compensation by the AO system. We propose a method to estimate the aberration from measurements by a single camera, by assuming that the aberration evolves according to (non-specific) model, i.e. the dynamics are contained in a model-set. At the same time that we estimate the aberration, we also identify the dynamics according to which the aberration evolves over time. The estimation of the wavefront aberration based on images of an unknown object is called blind deconvolution if both the aberration and object are estimated. Like phase retrieval, this too is a highly nonlinear estimation problem. We propose the first convexoptimization based estimation method for blind deconvolution problems that estimate aberration and object when the images are acquired using coherent illumination. The method allows for the inclusion of many existing types of prior information on the object and/or aberration. Finally, we analyze controllers for segmented mirrors in large ground-based telescopes. These mirrors consist of many interconnected hexagonal segments. This distributed nature of the system warrants the investigation into whether the controller that keeps the segments aligned can be designed in such a way that it can be distributed over the segments as well, essentially resulting in a distributed controller where local controllers communicate with each other. What complicates the analysis is that the dynamics across segments are not necessarily decoupled: the wind load can be correlated and the flexibility in the supporting structure of the segments can cause dynamic coupling. We investigate the design of a distributed controller that incorporates these global dynamics. Furthermore, we investigate the performance of the distributed controller and howit relates to the communication and Interconnection Pattern of the local controllers