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Since preserving data locality is very important in MapReduce frameworks, the placement of jobs' input data becomes critical for MapReduce job performance. However, existing data placement strategies applied in MapReduce based file systems lack the efficient control of data storage. Some input data of jobs may concentrate in a few nodes, making slots contention on those nodes more aggressive and thereby...
Free space optical(FSO) communication can provide high bandwidth, high security communication services. it is attractive for its convenient establish the communication link and low power consuming. As the active received area of optical fiber is very small, when using optical fiber technology in FSO system, we must consider the effects of angle of arrival. Tracking subsystem is an effective method...
Airflow disturbance affected aerodynamics of aircraft between damping rings. In order to simulate this disturbance, extra-fluent field of damping rings aircraft was analyzed by Reynolds stress model (LLR-QI) in this paper. Numerical simulations results indicate that spaces between damping rings affected drag coefficient, and keep to test results, to based on improving firing accuracy of the aircraft.
When we use the free space optical(FSO) communication in the near-ground, it will be great influenced by the atmospheric turbulence. There are many studies on the effects of atmospheric turbulence in FSO. Recently gamma-gamma is a widely accepted model for the optical propagating through the atmosphere in normal and strong turbulence. In order to enhance bit error rate(BER) performance influenced...
In this paper, we propose a new scheme of time-diversity system using Optical Code Division Multiple Access (OCDMA) in free space optical (FSO) communication. Our design is a fully-optical communication system which facilitates synthesizing the time-diversity signals. We found that it can effectively minimize the influence of scintillation caused by atmospheric turbulence. We analyze the bit error...
The performance of a satellite-to-ground optical communication system with phase modulation is limited by phase fluctuations induced by atmospheric turbulence. To improve the system performance, one effective way is to use coherent detection. In this paper, a satellite-to-ground coherent optical communication system with differential quadrature phase-shift keying (DQPSK) modulation is studied, and...
Application of very fast image detectors to the fine tracking system of free space optical (FSO) communication has been demonstrated in several projects. In the near surface of the earth, the influence of the atmosphere on the optical communication system must be considered. The optical communication system must be designed to be able to suppress the influence of atmospheric turbulence. We have used...
It's difficult to find contact from the image that was photographed by high-speed image sampling system because of the light reflection characteristic of switching arc, contact and interrupter. It do enhancement process to arc image by image enhancement algorithm of histogram and local histogram. In order to find the arc image and on the same time can find contact and the interrupupter's detail in...
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