1,721,437 research outputs found
A.Y.2014. Evolutionary Scheduling of Dynamic Multitasking Workloads for Big-Data Analytics in Elastic Cloud," Emerging Topics in Computing
No full textABSTRACT Scheduling of dynamic and multitasking workloads for big-data analytics is a challenging issue, as it requires a significant amount of parameter sweeping and iterations. Therefore, real-time scheduling becomes essential to increase the throughput of many-task computing. The difficulty lies in obtaining a series of optimal yet responsive schedules. In dynamic scenarios, such as virtual clusters in cloud, scheduling must be processed fast enough to keep pace with the unpredictable fluctuations in the workloads to optimize the overall system performance. In this paper, ordinal optimization using rough models and fast simulation is introduced to obtain suboptimal solutions in a much shorter timeframe. While the scheduling solution for each period may not be the best, ordinal optimization can be processed fast in an iterative and evolutionary way to capture the details of big-data workload dynamism. Experimental results show that our evolutionary approach compared with existing methods, such as Monte Carlo and Blind Pick, can achieve higher overall average scheduling performance, such as throughput, in real-world applications with dynamic workloads. Furthermore, performance improvement is seen by implementing an optimal computing budget allocating method that smartly allocates computing cycles to the most promising schedules. INDEX TERMS Big-data, cloud computing, evolutionary ordinal optimization, multitasking workload, virtual clusters
Multipath Routing over Wireless Mesh Networks For Multiple Description Video Transmission
No full textAbstract-In the past few years, wireless mesh networks (WMNs) have drawn significant attention from academia and industry as a fast, easy, and inexpensive solution for broadband wireless access. In WMNs, it is important to support video communications in an efficient way. To address this issue, this paper studies the multipath routing for multiple description (MD) video delivery over IEEE 802.11 based WMN. Specifically, we first design a framework to transmit MD video over WMNs through multiple paths; we then investigate the technical challenges encountered. In our proposed framework, multipath routing relies on the maximally disjoint paths to achieve good traffic engineering performance. However, video applications usually have strict delay requirements, which make it difficult to find multiple qualified paths with the least joints. To overcome this problem, we develop an enhanced version of Guaranteed-Rate (GR) packet scheduling algorithm, namely virtual reserved rate GR (VRR-GR), to shorten the packet delay of video communications in multiservice network environment. Simulation study shows that our proposed approach can reduce the latency of video delivery and achieve desirable traffic engineering performance in multipath routing environment
Small-Signal Stability Analysis of a DFIG-Based Wind Power System Under Different Modes of Operation
No full textAbstract-This paper focuses on the super/subsynchronous operation of the doubly fed induction generator (DFIG) system. The impact of a damping controller on the different modes of operation for the DFIG-based wind generation system is investigated. The coordinated tuning of the damping controller to enhance the damping of the oscillatory modes using bacteria foraging technique is presented. The results from eigenvalue analysis are presented to elucidate the effectiveness of the tuned damping controller in the DFIG system. The robustness issue of the damping controller is also investigated
A Synthetic Test Circuit for Current Switching Tests of HVDC Circuit Breakers
No full textAbstract -High voltage direct current (HVDC) circuit breaker current switching test in a test laboratory is difficult due to the limited test power installation. Reproduction of test stresses by means of direct testing confronts huge investment. Synthetic testing, as an alternative method, could amplify the test power more than ten times with a relative low cost. A synthetic test circuit based on the most used parallel current injection method was developed for the current switching test of HVDC circuit breakers. This synthetic test circuit could reproduce the current and voltage stresses equal to or greater than those could meet in service
Spectral domain immitance approach for dispersion characteristics of generalized printed transmission lines
Get PDFAbstract-A simple method for formofating the dyadic Green's functions in the spectral domain is presented for generalized printed traaaroiasion fines wbieh contain severaf dielectric layers and conductors appearing at several dielectric interfaa+s. The method is based on the transverse equivalent tranamiwion line for a spectraf wave and on a simple coordinate transformation. Tfds formulation process is so simple that often it is accompfiibed afmost by inspection of the physicaf cross-aectionaf sbwture of the transmission fine. Tbe method is applied to a new versatile transmission Iinq a mfcrastrfp-slot~me, and some numerical results are presented
Case Study of a Multi-Infeed HVDC System
No full textAbstract-There are serious concerns relating to a MultiInfeed HVDC system when feeding a weak AC network. Typical issues concerning multi-infeed configurations are: need for coordination of the recovery control, need for different DC modulation strategies to stabilize the system, possibility of voltage instability of the area receiving large amount of power from multiple HVDC links and the risk of mutual commutation failures. In contrast, if the area receiving electrical power from multiple HVDC transmission links is relatively strong due to the presence of large amount of generation units nearby there are still some questions that need to be investigated such as the issues underlining the operation of such a multi-infeed system, the proper design of the controls of the HVDC systems and the system dynamic performance under extreme contingencies. This paper investigates into an example of such a multi-infeed HVDC system. The authors have performed small signal analysis of the system to assess instability associated with the control modes. Electromechanical and voltage stability analysis were performed for harmful contingencies. Dynamic performance analysis was also carried out to analyze the interaction amongst various HVDC inverters during disturbances
Deep Learning Framework for Detection of Hypoglycemic Episodes in Children with Type 1 Diabetes*
No full textAbstract-Most Type 1 diabetes mellitus (T1DM) patients have hypoglycemia problem. Low blood glucose, also known as hypoglycemia, can be a dangerous and can result in unconsciousness, seizures and even death. In recent studies, heart rate (HR) and correct QT interval (QTc) of the electrocardiogram (ECG) signal are found as the most common physiological parameters to be effected from hypoglycemic reaction. In this paper, a state-of-the-art intelligent technology namely deep belief network (DBN) is developed as an intelligent diagnostics system to recognize the onset of hypoglycemia. The proposed DBN provides a superior classification performance with feature transformation on either processed or un-processed data. To illustrate the effectiveness of the proposed hypoglycemia detection system, 15 children with Type 1 diabetes were volunteered overnight. Comparing with several existing methodologies, the experimental results showed that the proposed DBN outperformed and achieved better classification performance
IEC 61850 Source Code Implementation for Accessing IED Data
No full textAbstract: Substations are opting IEC 61850 (International Electrotechnical Commission) interoperable protocol as the protocol helps in resolving most of the challenges related to IED (Intelligent Electronic Device) integration for providing an interoperable communication at bay level. However, it is still challenging for client applications to acquire data from IEC 61850 compliant IEDs and do further processing. The aim of this paper is to demonstrate how an IEC 61850 source code application running at station level can be configured to acquire data from the IEDs installed at bay level. The paper also describes the role of Manufacturing Message Specification (MMS) in establishing a communication between the client and the server (IED)
The higher order modal characteristics of circular-rectangular coaxial waveguides
No full textAbstract-A rigorous analysis combining the orthogonal expansion method and Galerkin method for the higher order eigenmodes in a circular-rectangular (C-R) waveguide is presented in this paper. The Bessel-Fourier series is employed to merge the circular and rectangular coordinate systems used in the analysis. The cutoff frequencies of the higher order modes are determined with the singular value decomposition (SVD) technique. The computed results are in excellent agreement with results obtained using the finite element method. Because of its analytic form, the solution will be useful in the rigorous analysis of many practical microwave components and circuits
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