Search results for "Distributed"

Object Clustering Methods and a Query Decomposition Strategy for Distributed Object-Based Information Systems

1999

Emerging developments and advances in distributed processing have created a need for tools and methods to partition and distribute information systems across interconnected processors. In particular, distribution approaches which take into account the key characteristics of OO concepts are required to extend traditional fragmentation results to object oriented database systems. To fulfill the above requirements, we propose a methodology for the distribution design of object-based information systems. The underlying approach consists of techniques and heuristics that can be used to create clusters of inter-related object classes that can be fragmented interdependently, producing distribution…

Accelerating data queries on Hadoop framework by using compact data formats

2016

There are massive amounts of data generated from IoT, online transactions, click streams, emails, logs, posts, social networking interactions, sensors, mobile phones and their applications etc. The question is where and how to store these data in order to provide faster data access. Understanding and handling Big Data is a big challenge. The research direction in Big Data projects using Hadoop Technology, MapReduce kind of framework and compact data formats such as RCFile, SequenceFile, ORC, Avro, Parquet shows that only two data formats (Avro and Parquet) support schema evolution and compression in order to utilize less storage space. In this paper, file formats like Avro and Parquet are c…

Infiniviz: Taking Quake 3 Arena on a Large-Scale Display System to the Next Level

2018

The authors of this paper have previously presented a large-scale display system called Infiniviz in other publications. Infiniviz attempts to improve network bandwidth consumption and computational performance compared to other existing large-scale display systems. Since the previous publications have been made in early development stages of Infiniviz, only the overview of the software architecture and details of hardware implementation have been presented so far. This paper contains a real-life test of Infiniviz running Quake 3 Arena at a resolution of 9600 x 5400 at 24 fps. Also, in this paper, the authors have tried to match their results to what has been published by other researchers …

HybridS: A Scheme for Secure Distributed Data Storage in WSNs

2008

In unattended wireless sensor networks (WSNs), data is stored locally or at designated nodes upon sensing, and users can access it on demand. This paradigm can improve energy efficiency by making use of the upcoming cheap and large flash memory, as well as system robustness. Nevertheless, the security and dependability of distributed storage are critical for the applicability of such WSNs. In this paper, we propose a secure and dependable data storage scheme by taking advantages of secret sharing and Reed-Solomon code, which has computational security and yet maintains optimal data size. The extensive analysis verifies our scheme can provide secure and dependable data storage in WSNs in the…

A recognize-and-accuse policy to speed up distributed processes

1994

Topic 5: Parallel and Distributed Data Management

2013

Nowadays we are facing an exponential growth of new data that is overwhelming the capabilities of companies, institutions and the society in general to manage and use it in a proper way. Ever-increasing investments in Big Data, cutting edge technologies and the latest advances in both application development and underlying storage systems can help dealing with data of such magnitude. Especially parallel and distributed approaches will enable new data management solutions that operate effectively at large scale.

Results of a literature review on methods for estimating buildings energy demand at district level

2019

Abstract In the framework of distributed energy planning, evaluating reliable energy profiles of different sectors has a prominent role. At the same time, it is a quite challenging task, since the availability of actual energy profiles of buildings at the district level is not widespread. A survey of over 70 studies in scientific literature has been accomplished and a set of criteria has been defined for classifying the selected contributions based on the energy demand data features, source and/or estimation methods, highlighting the ones adopting hourly energy profiles. As final results, tables summarizing the main methods characteristics and a selection of studies providing directly useab…

A distributed model for continuous-wave erbium-doped fiber laser

2011

Abstract A distributed model of a continuous-wave erbium-doped fiber laser is discussed. The model is based on two contra-propagated traveling laser waves, and includes inhomogeneous pumping, excited state absorption at the pump and the laser wavelengths, amplified spontaneous emission and radial distribution of populations of erbium levels. It is shown that excited state absorption is a main limiting factor to the laser's efficiency. Moreover, consideration of radial distributions of erbium levels' populations in the model reduces laser efficiency and decreases optimal reflection of the laser output coupler. The modeling results are in excellent agreement with the experimental study on the…

High-efficiency Q-switched erbium fiber laser using a Bragg grating-based modulator

2002

Abstract In this work we analyze the behavior of an erbium-doped fiber laser which is based on a simple scheme. Excitation of the active medium is performed in the 980 nm pump band with a CW semiconductor laser source. Two fiber Bragg gratings acting as mirrors of the Fabry–Perot laser cavity were used. One of these gratings was mounted over a piezoelectric (PZT) element. By applying voltage pulses to the piezoelectric, the laser cavity was temporally modulated and Q-switched laser pulses up to 530 mW peak powers at 3 kHz were obtained. Typical laser emission of 2–3 μs temporal widths and 0.1 nm of optical bandwidth have been achieved when the system was operated at 18.5 kHz repetition rate…

Single-frequency active Q-switched Distributed Fiber Laser Using Acoustic Waves

2007

This letter presents a single mode, actively Q-switched distributed feedback fiber laser. Acoustic pulses are launched into an erbium-doped fiber Bragg grating, resulting in the introduction of a traveling defect. Thus, a transmission peak appears in the reflection band while the pulse travels along the grating. This effect allows the laser to operate in a Q-switched regime, providing optical pulses which repetition rate was continuously tuned up to 10 kHz. Pulses of 168 mW of peak power and 73 ns of temporal width were obtained at low repetition rate.