MapReduce is an important programming model for building data centers containing ten of thousands of nodes. In a practical data center of that scale, it is a common case that I/Obound jobs and CPU-bound jobs, which demand different resources, run simultaneously in the same cluster. In the MapReduce framework, parallelization of these two kinds of job has not been concerned. In this paper, we give a new view of the MapReduce model, and classify the MapReduce workloads into three categories based on their CPU and I/O utilization. With workload classification, we design a new dynamic MapReduce workload predict mechanism, MR-Predict, which detects the workload type on the fly. We propose a Triple-Queue Scheduler based on the MR-Predict mechanism. The Triple-Queue scheduler could improve the usage of both CPU and disk I/O resources under heterogeneous workloads. And it could improve the Hadoop throughput by about 30% under heterogeneous workloads.
The statistical law that governs the drift velocity of tropical cyclones in the Northwest Pacific Ocean is investigated. The investigation is based on data published by China Meteorological Administration for historical tracks of 2146 cyclone events that occurred during 1949-2012. Empirical formulae are obtained to relate the magnitude, the direction, the meridional and zonal components of the averaged cyclone drift velocity with latitude. As the latitude effect is excluded, it is found that the cyclone drift velocity is governed by simple statistical laws, i.e. the magnitude and direction of the deviated drift velocity approximately satisfy a gamma distribution and a symmetric bimodal distribution, respectively, while the meridional and zonal components of the deviated drift velocity satisfy the same type of symmetric probability distribution represented by the hyperbolic secant function but with different deviations. The results obtained are potentially applicable to the enhancement of current tropical cyclone track forecasting techniques. They are also useful in risk management over the coastal areas where tropical cyclones may cause serious damages.
Background: The dose of radiation a patient receives when undergoing dual-energy computed tomography (CT) is of significant concern to the medical community, and balancing the tradeoffs between the level of radiation used and the quality of CT images is challenging. This paper proposes a method of synthesizing high-energy CT (HECT) images from low-energy CT (LECT) images using a neural network that achieves an alternative to HECT scanning by employing an LECT scan, which greatly reduces the radiation dose a patient receives.Methods: In the training phase, the proposed structure cyclically generates HECT and LECT images to improve the accuracy of extracting edge and texture features. Specifically, we combine multiple connection methods with channel attention (CA) and pixel attention (PA) mechanisms to improve the network's mapping ability of image features. In the prediction phase, we use a model consisting of only the network component that synthesizes HECT images from LECT images.Results: Our proposed method was conducted on clinical hip CT image data sets from Guizhou Provincial People's Hospital. In a comparison with other available methods [a generative adversarial network (GAN), a residual encoder-to-decoder network with a visual geometry group (VGG) pretrained model (RED-VGG), a Wasserstein GAN (WGAN), and CycleGAN] in terms of metrics of peak signal-to-noise ratio (PSNR), structural similarity index measure (SSIM), normalized mean square error (NMSE), and a visual effect evaluation, the proposed method was found to perform better on each of these evaluation criteria. Compared with the results produced by CycleGAN, the proposed method improved the PSNR by 2.44%, the SSIM by 1.71%, and the NMSE by 15.2%. Furthermore, the differences in the statistical indicators are statistically significant, proving the strength of the proposed method.
Conclusions:The proposed method synthesizes high-energy CT images from low-energy CT images, which significantly reduces both the cost of treatment and the radiation dose received by patients. Based on both image quality score metrics and visual effects comparisons, the results of the proposed method are superior to those obtained by other methods. 2 Zhou et al. Synthesis of high-energy CT images
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