4,067 research outputs found
Using Effective Generator Impedance for Forced Oscillation Source Location
Locating the sources of forced low-frequency oscillations in power systems is
an important problem. A number of proposed methods demonstrate their practical
usefulness, but many of them rely on strong modeling assumptions and provide
poor performance in certain cases for reasons still not well understood. This
paper proposes a systematic method for locating the source of a forced
oscillation by considering a generator's response to fluctuations of its
terminal voltages and currents. It is shown that a generator can be represented
as an effective admittance matrix with respect to low-frequency oscillations,
and an explicit form for this matrix, for various generator models, is derived.
Furthermore, it is shown that a source generator, in addition to its effective
admittance, is characterized by the presence of an effective current source
thus giving a natural qualitative distinction between source and nonsource
generators. Detailed descriptions are given of a source detection procedure
based on this developed representation, and the method's effectiveness is
confirmed by simulations on the recommended testbeds (eg. WECC 179-bus system).
This method is free of strong modeling assumptions and is also shown to be
robust in the presence of measurement noise and generator parameter
uncertainty.Comment: 13 page
Advanced flight control system study
A fly by wire flight control system architecture designed for high reliability includes spare sensor and computer elements to permit safe dispatch with failed elements, thereby reducing unscheduled maintenance. A methodology capable of demonstrating that the architecture does achieve the predicted performance characteristics consists of a hierarchy of activities ranging from analytical calculations of system reliability and formal methods of software verification to iron bird testing followed by flight evaluation. Interfacing this architecture to the Lockheed S-3A aircraft for flight test is discussed. This testbed vehicle can be expanded to support flight experiments in advanced aerodynamics, electromechanical actuators, secondary power systems, flight management, new displays, and air traffic control concepts
Model Predictive Control Based Trajectory Generation for Autonomous Vehicles - An Architectural Approach
Research in the field of automated driving has created promising results in
the last years. Some research groups have shown perception systems which are
able to capture even complicated urban scenarios in great detail. Yet, what is
often missing are general-purpose path- or trajectory planners which are not
designed for a specific purpose. In this paper we look at path- and trajectory
planning from an architectural point of view and show how model predictive
frameworks can contribute to generalized path- and trajectory generation
approaches for generating safe trajectories even in cases of system failures.Comment: Presented at IEEE Intelligent Vehicles Symposium 2017, Los Angeles,
CA, US
Dynamic Virtual Page-based Flash Translation Layer with Novel Hot Data Identification and Adaptive Parallelism Management
Solid-state disks (SSDs) tend to replace traditional motor-driven hard disks in high-end storage devices in past few decades. However, various inherent features, such as out-of-place update [resorting to garbage collection (GC)] and limited endurance (resorting to wear leveling), need to be reduced to a large extent before that day comes. Both the GC and wear leveling fundamentally depend on hot data identification (HDI). In this paper, we propose a hot data-aware flash translation layer architecture based on a dynamic virtual page (DVPFTL) so as to improve the performance and lifetime of NAND flash devices. First, we develop a generalized dual layer HDI (DL-HDI) framework, which is composed of a cold data pre-classifier and a hot data post-identifier. Those can efficiently follow the frequency and recency of information access. Then, we design an adaptive parallelism manager (APM) to assign the clustered data chunks to distinct resident blocks in the SSD so as to prolong its endurance. Finally, the experimental results from our realized SSD prototype indicate that the DVPFTL scheme has reliably improved the parallelizability and endurance of NAND flash devices with improved GC-costs, compared with related works.Peer reviewe
Supporting the Refinement of Clinical Process Models to Computer-Interpretable Guideline Models
Clinical guidelines contain recommendations on the appropriate management of patients with specific clinical conditions. A prerequisite for using clinical guidelines in information systems is to encode them in a Computer-Interpretable Guideline (CIG) language. However, this is a difficult and demanding task, usually done by IT staff. The goal of the paper is to facilitate the encoding of clinical guidelines in CIG languages, while increasing the involvement of clinicians. To achieve this, it is proposed to support the refinement of guideline processes from a preliminary specification in a business process language to a detailed implementation in one of the available CIG languages. The approach relies on the use of the Business Process Model and Notation (BPMN) for the specification level, a CIG language for the implementation level, and on algorithms to semi-automatically transform guideline models in BPMN into the CIG language of choice. As a first step towards the implementation of the approach, in this work algorithms are implemented to transform a BPMN specification of clinical processes into the PROforma CIG language, and are successfully applied to several clinical guidelines
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