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  • Other Sources  (42)
  • Computer Systems  (28)
  • Electronics and Electrical Engineering  (8)
  • Numerical Analysis  (6)
  • Electronic structure and strongly correlated systems
  • Chemistry
  • 1
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    A Model-based Prognostics Methodology for Electrolytic Capacitors Based on Electrical Overstress Accelerated Aging (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-27
    Description: A remaining useful life prediction methodology for electrolytic capacitors is presented. This methodology is based on the Kalman filter framework and an empirical degradation model. Electrolytic capacitors are used in several applications ranging from power supplies on critical avionics equipment to power drivers for electro-mechanical actuators. These devices are known for their comparatively low reliability and given their criticality in electronics subsystems they are a good candidate for component level prognostics and health management. Prognostics provides a way to assess remaining useful life of a capacitor based on its current state of health and its anticipated future usage and operational conditions. We present here also, experimental results of an accelerated aging test under electrical stresses. The data obtained in this test form the basis for a remaining life prediction algorithm where a model of the degradation process is suggested. This preliminary remaining life prediction algorithm serves as a demonstration of how prognostics methodologies could be used for electrolytic capacitors. In addition, the use degradation progression data from accelerated aging, provides an avenue for validation of applications of the Kalman filter based prognostics methods typically used for remaining useful life predictions in other applications.
    Keywords: Electronics and Electrical Engineering
    Type: ARC-E-DAA-TN3987 , Annual Conference of the PHM Society 2011; 25-29 Sept. 2011; Montreal/Canada; United States
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  • 2
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    Using Multithreading for the Automatic Load Balancing of 2D Adaptive Finite Element Meshes (1998)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: In this paper, we present a multi-threaded approach for the automatic load balancing of adaptive finite element (FE) meshes. The platform of our choice is the EARTH multi-threaded system which offers sufficient capabilities to tackle this problem. We implement the question phase of FE applications on triangular meshes, and exploit the EARTH token mechanism to automatically balance the resulting irregular and highly nonuniform workload. We discuss the results of our experiments on EARTH-SP2, an implementation of EARTH on the IBM SP2, with different load balancing strategies that are built into the runtime system.
    Keywords: Numerical Analysis
    Type: 5th International Symposium on Solving Irregularly Structured Problems in Parallel; Aug 09, 1998 - Aug 11, 1998; Berkley, CA; United States
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  • 3
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    A Hierarchical and Distributed Approach for Mapping Large Applications to Heterogeneous Grids using Genetic Algorithms (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In this paper, we propose a distributed approach for mapping a single large application to a heterogeneous grid environment. To minimize the execution time of the parallel application, we distribute the mapping overhead to the available nodes of the grid. This approach not only provides a fast mapping of tasks to resources but is also scalable. We adopt a hierarchical grid model and accomplish the job of mapping tasks to this topology using a scheduler tree. Results show that our three-phase algorithm provides high quality mappings, and is fast and scalable.
    Keywords: Computer Systems
    Type: IEEE 5th International Conference on Cluster Computing; Dec 01, 2003 - Dec 04, 2003; Hong Kong; China
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  • 4
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    PLUM: Parallel Load Balancing for Adaptive Unstructured Meshes (1998)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Mesh adaption is a powerful tool for efficient unstructured-grid computations but causes load imbalance among processors on a parallel machine. We present a novel method called PLUM to dynamically balance the processor workloads with a global view. This paper presents the implementation and integration of all major components within our dynamic load balancing strategy for adaptive grid calculations. Mesh adaption, repartitioning, processor assignment, and remapping are critical components of the framework that must be accomplished rapidly and efficiently so as not to cause a significant overhead to the numerical simulation. A data redistribution model is also presented that predicts the remapping cost on the SP2. This model is required to determine whether the gain from a balanced workload distribution offsets the cost of data movement. Results presented in this paper demonstrate that PLUM is an effective dynamic load balancing strategy which remains viable on a large number of processors.
    Keywords: Numerical Analysis
    Type: SIAM Annual Meeting; Jul 13, 1998 - Jul 17, 1998; Toronto; Canada
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  • 5
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    Ordering Unstructured Meshes for Sparse Matrix Computations on Leading Parallel Systems (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The ability of computers to solve hitherto intractable problems and simulate complex processes using mathematical models makes them an indispensable part of modern science and engineering. Computer simulations of large-scale realistic applications usually require solving a set of non-linear partial differential equations (PDES) over a finite region. For example, one thrust area in the DOE Grand Challenge projects is to design future accelerators such as the SpaHation Neutron Source (SNS). Our colleagues at SLAC need to model complex RFQ cavities with large aspect ratios. Unstructured grids are currently used to resolve the small features in a large computational domain; dynamic mesh adaptation will be added in the future for additional efficiency. The PDEs for electromagnetics are discretized by the FEM method, which leads to a generalized eigenvalue problem Kx = AMx, where K and M are the stiffness and mass matrices, and are very sparse. In a typical cavity model, the number of degrees of freedom is about one million. For such large eigenproblems, direct solution techniques quickly reach the memory limits. Instead, the most widely-used methods are Krylov subspace methods, such as Lanczos or Jacobi-Davidson. In all the Krylov-based algorithms, sparse matrix-vector multiplication (SPMV) must be performed repeatedly. Therefore, the efficiency of SPMV usually determines the eigensolver speed. SPMV is also one of the most heavily used kernels in large-scale numerical simulations.
    Keywords: Computer Systems
    Type: Irregular; May 01, 2000; Cancun; Mexico
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  • 6
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    A New Approach to Parallel Dynamic Partitioning for Adaptive Unstructured Meshes (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Classical mesh partitioning algorithms were designed for rather static situations, and their straightforward application in a dynamical framework may lead to unsatisfactory results, e.g., excessive data migration among processors. Furthermore, special attention should be paid to their amenability to parallelization. In this paper, a novel parallel method for the dynamic partitioning of adaptive unstructured meshes is described. It is based on a linear representation of the mesh using self-avoiding walks.
    Keywords: Computer Systems
    Type: IPPS''99; Apr 12, 1999 - Apr 16, 1999; San Juan; Puerto Rico
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  • 7
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    Physics Based Electrolytic Capacitor Degradation Models for Prognostic Studies under Thermal Overstress (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Electrolytic capacitors are used in several applications ranging from power supplies on safety critical avionics equipment to power drivers for electro-mechanical actuators. This makes them good candidates for prognostics and health management research. Prognostics provides a way to assess remaining useful life of components or systems based on their current state of health and their anticipated future use and operational conditions. Past experiences show that capacitors tend to degrade and fail faster under high electrical and thermal stress conditions that they are often subjected to during operations. In this work, we study the effects of accelerated aging due to thermal stress on different sets of capacitors under different conditions. Our focus is on deriving first principles degradation models for thermal stress conditions. Data collected from simultaneous experiments are used to validate the desired models. Our overall goal is to derive accurate models of capacitor degradation, and use them to predict performance changes in DC-DC converters.
    Keywords: Electronics and Electrical Engineering
    Type: ARC-E-DAA-TN5005 , First European Conference of the Prognostics and Health; Jul 03, 2012; Dresden; Germany
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  • 8
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    Prognostics of Power Electronics, Methods and Validation Experiments (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Abstract Failure of electronic devices is a concern for future electric aircrafts that will see an increase of electronics to drive and control safety-critical equipment throughout the aircraft. As a result, investigation of precursors to failure in electronics and prediction of remaining life of electronic components is of key importance. DC-DC power converters are power electronics systems employed typically as sourcing elements for avionics equipment. Current research efforts in prognostics for these power systems focuses on the identification of failure mechanisms and the development of accelerated aging methodologies and systems to accelerate the aging process of test devices, while continuously measuring key electrical and thermal parameters. Preliminary model-based prognostics algorithms have been developed making use of empirical degradation models and physics-inspired degradation model with focus on key components like electrolytic capacitors and power MOSFETs (metal-oxide-semiconductor-field-effect-transistor). This paper presents current results on the development of validation methods for prognostics algorithms of power electrolytic capacitors. Particularly, in the use of accelerated aging systems for algorithm validation. Validation of prognostics algorithms present difficulties in practice due to the lack of run-to-failure experiments in deployed systems. By using accelerated experiments, we circumvent this problem in order to define initial validation activities.
    Keywords: Electronics and Electrical Engineering
    Type: ARC-E-DAA-TN7926 , IEEE Autotestcon; Sep 10, 2012 - Sep 12, 2012; Anaheim, CA; United States
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  • 9
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    Physics Based Modeling and Prognostics of Electrolytic Capacitors (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper proposes first principles based modeling and prognostics approach for electrolytic capacitors. Electrolytic capacitors have become critical components in electronics systems in aeronautics and other domains. Degradations and faults in DC-DC converter unit propagates to the GPS and navigation subsystems and affects the overall solution. Capacitors and MOSFETs are the two major components, which cause degradations and failures in DC-DC converters. This type of capacitors are known for its low reliability and frequent breakdown on critical systems like power supplies of avionics equipment and electrical drivers of electromechanical actuators of control surfaces. Some of the more prevalent fault effects, such as a ripple voltage surge at the power supply output can cause glitches in the GPS position and velocity output, and this, in turn, if not corrected will propagate and distort the navigation solution. In this work, we study the effects of accelerated aging due to thermal stress on different sets of capacitors under different conditions. Our focus is on deriving first principles degradation models for thermal stress conditions. Data collected from simultaneous experiments are used to validate the desired models. Our overall goal is to derive accurate models of capacitor degradation, and use them to predict performance changes in DC-DC converters.
    Keywords: Electronics and Electrical Engineering
    Type: ARC-E-DAA-TN5352 , AIAA @ Infotec 2012; Jun 19, 2012 - Jun 21, 2012; Garden Grove, CA; United States
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  • 10
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    Bayesian Framework Approach for Prognostic Studies in Electrolytic Capacitor under Thermal Overstress Conditions (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Electrolytic capacitors are used in several applications ranging from power supplies for safety critical avionics equipment to power drivers for electro-mechanical actuator. Past experiences show that capacitors tend to degrade and fail faster when subjected to high electrical or thermal stress conditions during operations. This makes them good candidates for prognostics and health management. Model-based prognostics captures system knowledge in the form of physics-based models of components in order to obtain accurate predictions of end of life based on their current state of heal th and their anticipated future use and operational conditions. The focus of this paper is on deriving first principles degradation models for thermal stress conditions and implementing Bayesian framework for making remaining useful life predictions. Data collected from simultaneous experiments are used to validate the models. Our overall goal is to derive accurate models of capacitor degradation, and use them to remaining useful life in DC-DC converters.
    Keywords: Electronics and Electrical Engineering
    Type: ARC-E-DAA-TN5953 , Annual Conference of the PHM Society 2012; Sep 23, 2012 - Sep 27, 2012; Minneapolis, MN; United States
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