Data Replication and Its Alignment with Fault Management in the Cloud Environment

Nowadays, the exponential data growth becomes one of the major challenges all over the world. It may cause a series of negative impacts such as network overloading, high system complexity, and inadequate data security, etc. Cloud computing is developed to construct a novel paradigm to alleviate massive data processing challenges with its on-demand services and distributed architecture. Data replication has been proposed to strategically distribute the data access load to multiple cloud data centres by creating multiple data copies at multiple cloud data centres. A replica-applied cloud environment not only achieves a decrease in response time, an increase in data availability, and more balanced resource load but also protects the cloud environment against the upcoming faults. The reactive fault tolerance strategy is also required to handle the faults when the faults already occurred. As a result, the data replication strategies should be aligned with the reactive fault tolerance strategies to achieve a complete management chain in the cloud environment. In this thesis, a data replication and fault management framework is proposed to establish a decentralised overarching management to the cloud environment. Three data replication strategies are firstly proposed based on this framework. A replica creation strategy is proposed to reduce the total cost by jointly considering the data dependency and the access frequency in the replica creation decision making process. Besides, a cloud map oriented and cost efficiency driven replica creation strategy is proposed to achieve the optimal cost reduction per replica in the cloud environment. The local data relationship and the remote data relationship are further analysed by creating two novel data dependency types, Within-DataCentre Data Dependency and Between-DataCentre Data Dependency, according to the data location. Furthermore, a network performance based replica selection strategy is proposed to avoid potential network overloading problems and to increase the number of concurrent-running instances at the same time

Comparison of predicted and experimentally determined ablation area for penetrating electrodes configuration.

Panels 1–9 show sections of a lesion that has been stained with tetrazolium chloride (TTC), so that the ablated areas are white, while the surviving areas are stained red. We used the outline from Fig 6B as the theoretical prediction and oriented it so that the electrodes in the simulation match the electrodes in the experiment; the resulting outline is superimposed in green over each stained section.</p

Contributions of the field components to the norm of the field for isotropic conditions (<i>a</i> = 1) and strongly anisotropic conditions (<i>a</i> = 10) using parameter set 1.

<p>The figure shows a zoom into the area around the electrodes, not the complete (circular) medium.</p

Predicted ablated volume for parameter set 2 and epi-endo electrode configuration.

<p>A: Epi-endo geometry. Red surface is isosurface for |E| = 3kV/cm. B: Oblique view. C: Top view. D: Side view. E: Width variability function.</p

Predicted ablated volume for parameter set 4 epi-endo configuration.

<p>Details as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0152262#pone.0152262.g010" target="_blank">Fig 10</a>. Amplitude of applied voltage is 2.3 kV.</p

Predicted ablated volume for parameter set 4 and penetrating electrodes configuration.

<p>Details as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0152262#pone.0152262.g010" target="_blank">Fig 10</a>. Amplitude of applied voltage is 1.8 kV.</p

Parameter sets used in numerical simulations.

Parameter sets used in numerical simulations.</p

N‑Doped Carbon Nanotube Shell Encapsulating the NiFe Metal Core for Enhanced Catalytic Stability in Methanol Oxidation Reaction by the Structural Cooperation Mechanism

Exploitation of high-efficiency catalysts toward methanol oxidation is a pivotal step to promote the commercialization of direct methanol fuel cells. Herein, a strategy is demonstrated to prepare nitrogen-doped carbon nanotubes with NiFe metal particles (NiFe@N-CNT) as the carrier material of Pt nanoparticles. Combining SEM and TEM, NiFe metal particles are fully encapsulated in N-CNTs, and they form the metal core and carbon nanotube shell structure based on the structural cooperation mechanism. Surprisingly, the as-prepared Pt/NiFe@N-CNT catalyst shows superior catalytic activity (1023 mA mg–1Pt) compared to commercial Pt/C (392 mA mg–1Pt), Pt/Ni@N-CNT (331 mA mg–1Pt), and Pt/Fe@N-CNT (592 mA mg–1Pt). After 1000 cycles, Pt/NiFe@N-CNT maintains the optimal catalytic activity (588 mA mg–1Pt), and its mass activity loss is 42.5%, which is better than those of commercial Pt/C (64.0%), Pt/Ni@N-CNT (67.7%), and Pt/Fe@N-CNT (59.6%) catalysts, indicating that the Pt/NiFe@N-CNT catalyst achieves excellent catalytic activity and stability, which stems chiefly from the homodispersed Pt nanoparticles and the generation of the metal core–carbon nanotube shell based on the structural cooperation mechanism. This study reports the facile construction of a metal core–carbon nanotube shell structure, which intrinsically ameliorates structural collapse of carrier material, thereby improving the catalytic stability of the Pt-based catalyst and broadening the view for design of other desire catalysts in methanol oxidation

Effect of fiber angle on field distribution for strong anisotropy (<i>a</i> = 10) using parameter set 1.

<p>A: <i>α</i> = 0°. B: <i>α</i> = 30°. C: <i>α</i> = 60°. D: <i>α</i> = 90°.</p

Geometry of our tissue model for the penetrating electrodes configuration.

<p>The tissue domain is cylindrical and the electrodes are placed symmetrically to the cylinder's axis. The tissue domain is discretized into tetrahedral elements (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0152262#pone.0152262.t001" target="_blank">Table 1</a> for details). Four of the 40 layers are marked blue (layers 0, 14, 25, and 39 from the epicardium), and the fiber orientation in these layers is illustrated and quantified on the right. The angle <i>α</i> is defined as the difference between the local fiber direction and the line through the points at which the electrodes intersect the layer.</p