With the development of cloud computing, more and more enterprises begin to develop their own cloud storage architecture by Hadoop. HDFS, at the bottom of Hadoop framework, stores files on all the nodes in cluster. This article first analyzed the HDFS architecture and put forward a problem single point of failure: There is only one NameNode in HDFS, which has limited the number of metadata storage and is prone to a failure of single node. Once the NameNode fault occurs, the system will break down. It affects the reliability of the cluster directly. Then it introduced Paxos algorithm and improved the structure of HDFS according to its principle. It solved the problem by increasing the number of NameNode and ensuring the synchronization of them by Paxos algorithm. At last, it verified the feasibility of the scheme by an experiment. A failure of metadata server will not interrupt the system so the reliability is improved.
Tungsten
bronze is an effective near-infrared (NIR) shielding material
for fabricating energy-saving smart windows. While high-performing
NIR-shielding glasses can be fabricated by coating a tungsten bronze
film on window glasses, these glasses suffer a short lifespan due
to the adhesion and degeneration of film. In this work, we show that
tungsten bronze-like material Na5W14O44 can be distributed in the bulk glass matrix during the facile melt-quenching
glass fabrication process under an air atmosphere, overcoming the
limitations of film-based glasses. X-ray diffraction, Raman spectroscopy,
and X-ray photoelectron spectroscopy confirmed the presence of tungsten
bronze-like Na5W14O44 functional
units in the SiO2–B2O3–NaF
glass matrix. The addition of a small amount of H2WO4 and Sb2O3 is critical for the formation
of Na5W14O44 functional units because
H2WO4 provides W for Na5W14O44, and Sb2O3 acts as a reducing
agent that helps the formation of W5+ in Na5W14O44 under an air atmosphere. Furthermore,
the NIR-shielding ability can be tuned by adjusting the concentration
of Sb2O3 in the range of 0–1.5 mol %
and of H2WO4 in the range of 4–6 mol
%. The optimized composition containing 1.25 mol % of Sb2O3 and 5 mol % of H2WO4 exhibits
excellent NIR-shielding ability (ΔT = 62.8%),
high visible light transmittance (T
max = 67.7%), and excellent thermal insulation. This performance is
comparable to cesium tungsten bronze film-based glasses and much better
than soda lime glass and ITO glass under sun irradiation. This study
sheds light on fabricating energy-saving windows in a simple and cost-effective
way with flexibility for fine tuning of NIR-shielding performance.
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