Access Control Based Resource Allocation in Cloud Computing Environment

Abstract In this paper, we propose a new dynamic resource allocation scheme -Access Control-based Resource Allocation (ACRA) for cloud users in order to address some deficiencies of the current resources allocation mechanisms in some free cloud computing environment. The proposed scheme comprehensively analyses behavior characteristics of cloud users and evaluates user behavior trust using fuzzy analytic hierarchy process (FAHP), and then dynamically adjusts the resources permission of cloud users according to their behavior trust values, thus effectively controlling user resource utilization. Experimental results show that the ACRA scheme can provide basis for allocating resources dynamically and reasonably to cloud users with different behaviors and improve resource utilization in cloud computing systems

Adsorption of dimethylarsinate (DMA) monomethylarsonate (MMA), and arsenate on Goethite (alpha-FeOOH)

Ph.DDOCTOR OF PHILOSOPH

Supercapacitor Electrodes Derived from Carbon Dioxide

This work presents an unprecedented capacitive performance of porous carbons synthesized from carbon dioxide (CO₂). CO₂ is specifically converted to boron-doped porous carbons (BPCs) by reaction with sodium borohydride (NaBH₄) at 1 atm and temperatures around 500 °C. The pristine BPCs subsequently undergo treatment steps of salt removal and potassium hydroxide (KOH) activation. The activated BPCs provide specific capacitance of 130–140 F/g in a neutral solution of 1 M Na₂SO₄ after several thousand cycles. Main contributing factors to the high capacitance of the activated BPCs are their large surface area and well-defined micropores induced by the KOH activation. The observations have been elucidated by various spectroscopic and microscopic analyses

Synthesis of Cellular Silica Using Microbubbles as Templates

In this work, cellular silica was synthesized by using microbubbles as templates, which contain a mixture of argon and silicon tetrafluoride (SiF4). The latter is generated from decomposition of hexafluorosilicic acid (H2SiF6) at ambient conditions. The specific surface area of cellular silica can be as high as 130 m2/g, the size of the cavity is hundreds-of-nanometers, and the thickness of the cavity wall is around 30 nm. The cavity size, apparent packing density, and porosity of cellular silica strongly depend on the nature of the aqueous solutions; the cavity size appears to be negatively proportional to the surface tension, but thickness of cavity walls seems to be weakly affected by the aqueous properties. An attempt was made to introduce aluminum atoms in situ in the second-coordination sphere of Si atoms and/or load aluminum into the silica structure. Cellular silica with large pores facilitate the transfer of large molecules, including polymers and enzymes; thus, it could find applications in (bio)catalysis, sorption, controlled release and separations

Oxygen release and reduction kinetics of La0.35Sr0.35Ba0.3Fe1-xCoxO3 as oxygen carriers for chemical looping dry reforming of methane

Chemical looping dry reforming of methane (CL-DRM) is a viable technology by converting CH4 and CO2 to various value-added products to achieve carbon neutrality. However, it is vital for the technology to find suitable oxygen carriers with high oxygen capacity and activity. La0.35Sr0.35Ba0.3Fe1-xCoxO3 perovskite-type oxides were proposed as oxygen carriers for CL-DRM. The oxygen (O2) release property and the kinetics of La0.35Sr0.35Ba0.3Fe1-xCoxO3 reduction by CH4 were investigated via thermogravimetric analysis, O2-temperature programmed desorption and then in a fixed-bed reactor. The O2 release process of La0.35Sr0.35Ba0.3Fe1-xCoxO3 OCs can be divided into two phases. The O2 release process and corresponding rate of OCs were facilitated due to the substitution of Fe with Co in B-site. The total amounts of O2 release for these OCs were enhanced about 1.5 times from 0.445 mmol/gOC to 0.706 mmol/gOC as Co atomic fraction in B-site changes from 0 to 1. The linear correlation for high temperature phase and a volcano-curve for low temperature phase was found for the correlations among total O2 release and Co content during the O2 release process. The reduction kinetics of CH4 over OCs was described using the Avrami–Erofe'ev model (A1.5 or A2). The values of apparent activation energy (Ea) for all OCs were obtained. The results indicated the best substitution proportion of Co in La0.35Sr0.35Ba0.3Fe1-xCoxO3 OCs can be set in the range of 0.2–0.4 to emerge the excellent redox performance. The kinetics models and parameters offer valuable information for CL-DRM reactor design and further development of OCs with different A or/and B-site modifications