The Experts below are selected from a list of 168 Experts worldwide ranked by ideXlab platform
T. Kittelmann - One of the best experts on this subject based on the ideXlab platform.
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NCrystal: A library for thermal neutron transport
Computer Physics Communications, 2020Co-Authors: Xiao Xiao Cai, T. KittelmannAbstract:Abstract An open source software package for modelling thermal neutron transport is presented. The code facilitates Monte Carlo-based transport simulations and focuses in the initial release on interactions in both mosaic single crystals as well as polycrystalline materials and powders. Both coherent elastic (Bragg diffraction) and incoherent or inelastic (phonon) scattering are modelled, using basic parameters of the crystal unit cell as input. Included is a data library of validated crystal definitions, standalone tools and interfaces for C++ , C and Python programming languages. Interfaces for two popular simulation packages, Geant4 and McStas , are provided, enabling highly realistic simulations of typical components at neutron scattering instruments, including beam filters, monochromators, analysers, samples, and detectors. All interfaces are presented in detail, along with the end-User Configuration procedure which is deliberately kept User-friendly and consistent across all interfaces. An overview of the relevant neutron scattering theory is provided, and the physics modelling capabilities of the software are discussed. Particular attention is given here to the ability to load crystal structures and form factors from various sources of input, and the results are benchmarked and validated against experimental data and existing crystallographic software. Good agreements are observed. Program summary Program Title: NCrystal Program Files doi: http://dx.doi.org/10.17632/s3rpb5d9j3.1 Licensing provisions: Apache License, Version 2.0 (for core NCrystal ). Programming language: C++ , C and Python External routines/libraries: Geant4 , McStas Nature of problem: Thermal neutron transport in structured materials is inadequately supported in popular Monte Carlo transport applications, preventing simulations of a range of otherwise interesting setups. Solution method: Provide models for thermal neutron transport in flexible open source library, to be used standalone or as backend in existing Monte Carlo packages. Facilitate validation and work sharing by making it possible to share material Configurations between supported applications.
Xiao Xiao Cai - One of the best experts on this subject based on the ideXlab platform.
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NCrystal: A library for thermal neutron transport
Computer Physics Communications, 2020Co-Authors: Xiao Xiao Cai, T. KittelmannAbstract:Abstract An open source software package for modelling thermal neutron transport is presented. The code facilitates Monte Carlo-based transport simulations and focuses in the initial release on interactions in both mosaic single crystals as well as polycrystalline materials and powders. Both coherent elastic (Bragg diffraction) and incoherent or inelastic (phonon) scattering are modelled, using basic parameters of the crystal unit cell as input. Included is a data library of validated crystal definitions, standalone tools and interfaces for C++ , C and Python programming languages. Interfaces for two popular simulation packages, Geant4 and McStas , are provided, enabling highly realistic simulations of typical components at neutron scattering instruments, including beam filters, monochromators, analysers, samples, and detectors. All interfaces are presented in detail, along with the end-User Configuration procedure which is deliberately kept User-friendly and consistent across all interfaces. An overview of the relevant neutron scattering theory is provided, and the physics modelling capabilities of the software are discussed. Particular attention is given here to the ability to load crystal structures and form factors from various sources of input, and the results are benchmarked and validated against experimental data and existing crystallographic software. Good agreements are observed. Program summary Program Title: NCrystal Program Files doi: http://dx.doi.org/10.17632/s3rpb5d9j3.1 Licensing provisions: Apache License, Version 2.0 (for core NCrystal ). Programming language: C++ , C and Python External routines/libraries: Geant4 , McStas Nature of problem: Thermal neutron transport in structured materials is inadequately supported in popular Monte Carlo transport applications, preventing simulations of a range of otherwise interesting setups. Solution method: Provide models for thermal neutron transport in flexible open source library, to be used standalone or as backend in existing Monte Carlo packages. Facilitate validation and work sharing by making it possible to share material Configurations between supported applications.
Sem Borst - One of the best experts on this subject based on the ideXlab platform.
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User-level performance of channel-aware scheduling algorithms in wireless data networks
IEEE ACM Transactions on Networking, 2005Co-Authors: Sem BorstAbstract:Channel-aware scheduling strategies, such as the Pro- portional Fair algorithm for theCDMA1xEV-DO system, provide an effective mechanism for improving throughput performance in wireless data networks by exploiting channel fluctuations. The performance of channel-aware scheduling algorithms has mostly been explored at the packet level for a static User population, often assuming infinite backlogs. In the present paper, we focus on the performance at the flow level in a dynamic setting with random finite-size service demands. We show that in certain cases the User-level performance may be evaluated by means of a multiclass Processor-Sharing model where the total service rate varies with the total number of Users. The latter model provides explicit formulas for the distribution of the number of active Users of the various classes, the mean response times, the blocking probabilities, and the throughput. In addition we show that, in the presence of channel variations, greedy, myopic strategies which maximize throughput in a static scenario, may result in sub-op- timal throughput performance for a dynamic User Configuration and cause potential instability effects.
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User level performance of channel aware scheduling algorithms in wireless data networks
CWI report. PNA-R : probability networks and algorithms, 2002Co-Authors: Sem BorstAbstract:Channel-aware scheduling strategies, such as the Proportional Fair algorithm for the CDMA 1xEV-DO system, provide an effective mechanism for improving throughput performance in wireless data networks by exploiting channel fluctuations. The performance of channel-aware scheduling algorithms has mostly been explored at the packet level for a static User population, often assuming infinite backlogs. In the present paper, we focus on the performance at the flow level in a dynamic setting with random finite-size service demands. We show that in certain cases the User-level performance may be evaluated by means of a multi-class Processor-Sharing model where the total service rate varies with the total number of Users. The latter model provides explicit formulas for the distribution of the number of active Users of the various classes, the mean response times, the blocking probabilities, and the mean throughput. In addition we show that, in the presence of channel variations, greedy, myopic strategies which maximize throughput in a static scenario, may result in sub-optimal throughput performance for a dynamic User Configuration and cause potential instability effects.
Matthew B Jones - One of the best experts on this subject based on the ideXlab platform.
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accelerating parameter sweep workflows by utilizing ad hoc network computing resources an ecological example
IEEE Congress on Services, 2009Co-Authors: Jianwu Wang, Ilkay Altintas, Parviez R Hosseini, Derik Barseghian, Daniel Crawl, Chad Berkley, Matthew B JonesAbstract:Making use of distributed execution within scientific workflows is a growing and promising methodology to achieve better execution performance. We have implemented a distributed execution framework in the Kepler scientific workflow environment, called Master-Slave Distribution, to distribute sub-workflows to a common distributed environment, namely ad-hoc network computing resources. For a typical parameter sweep workflow, this architecture can realize concurrent independent sub-workflow executions with minimal User Configuration, allowing large gains in productivity with little of the typical overhead associated with learning distributed computing systems. We explain details of the Master-Slave architecture and demonstrate its usability and time efficiency by a use case in the theoretical ecology domain. We also discuss the capabilities of this architecture under different computational domains in Kepler.
Giuseppe Caire - One of the best experts on this subject based on the ideXlab platform.
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performance analysis of massive mimo for cell boundary Users
IEEE Transactions on Wireless Communications, 2015Co-Authors: Chanbyoung Chae, Giuseppe CaireAbstract:In this paper, we consider massive multiple-input–multiple-output systems for both downlink and uplink scenarios, where three radio units connected via one digital unit support multiple User equipments at the cell-boundary through the same radio resource, i.e., the same time–frequency slot. For downlink transmitter options, the study considers zero forcing (ZF) and maximum ratio transmission (MRT), whereas for uplink receiver options, it considers ZF and maximum ratio combining (MRC). For the sum rate of each of these, we derive simple closed-form formulas. In the simple but practically relevant case where uniform power is allocated to all downlink data streams, we observe that, for the downlink, vector normalization is better for ZF whereas matrix normalization is better for MRT. For a given antenna and User Configuration, we also analytically derive the signal-to-noise-ratio level below which MRC should be used instead of ZF. Numerical simulations confirm our analytical results.
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performance analysis of massive mimo for cell boundary Users
arXiv: Information Theory, 2013Co-Authors: Yeongeun Lim, Chanbyoung Chae, Giuseppe CaireAbstract:In this paper, we consider massive multiple-input multiple-output (MIMO) systems for both downlink and uplink scenarios, where three radio units (RUs) connected via one digital unit (DU) support multiple User equipments (UEs) at the cell-boundary through the same radio resource, i.e., the same time-frequency slot. For downlink transmitter options, the study considers zero-forcing (ZF) and maximum ratio transmission (MRT), while for uplink receiver options it considers ZF and maximum ratio combining (MRC). For the sum rate of each of these, we derive simple closed-form formulas. In the simple but practically relevant case where uniform power is allocated to all downlink data streams, we observe that, for the downlink, vector normalization is better for ZF while matrix normalization is better for MRT. For a given antenna and User Configuration, we also derive analytically the signal-to-noise-ratio (SNR) level below which MRC should be used instead of ZF. Numerical simulations confirm our analytical results.
