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Multi-Tenant Data Storage Model and Performance Evaluation
Dun Li,Zhenfei Wang,Zhiyun Zheng,Jin Zhao 보안공학연구지원센터 2016 International Journal of Database Theory and Appli Vol.9 No.3
Multi-tenant data storage model has multiple solutions and comparing the different storage solutions can help users improve their work efficiency. This paper proposes a query performance evaluation method based on the relational algebra. First of all, we introduce three wide table models. Secondly, we unite the format of tenant query SQL statement by analyzing structure of storage model, replace the unified format SQL with the relational algebra and evaluate the I/O cost of SQL query using relational algebra. Finally, through theoretical calculations and experimental simulations, we evaluate the performance of multi-tenant storage model according to query performance. The results show our evaluation method based on relational algebra provides new perspective for the study of performance evaluation in multi-tenant data model.
Kinetics of perovskite-like oxygen carriers for chemical looping air separation
Limin Hou,Qingbo Yu,Tuo Wang,Kun Wang,Qin Qin,Zhenfei Qi 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.3
Chemical looping air separation gives an energy-efficient choice for oxygen production. We performed kinetic analysis of YBaCo4O7+δ, Y0.95Ti0.05BaCo4O7+δ, Y0.2Ti0.05Dy0.75BaCo4O7+δ, and Y0.15Zr0.1Dy0.75BaCo4O7+δ oxygen carriers in a CLAS process. TG experiments were conducted with heating rates of 0.5, 1, and 2 oC/min in a thermogravimetric analyzer. Further exploration is required to develop an appropriate oxygen carrier. So, we used the model-free approach, Starink method, to evaluate the apparent activation energy. And, masterplots method was applied to determine the most probable mechanism function. The results show that the distributed activation energies of oxidation/ reduction process are 189.42/286.22 kJ/mol, 197.70/324.87 kJ/mol, 195.41/310.4 kJ/mol, and 192.20/293.53 kJ/mol for YBaCo4O7+δ, Y0.95Ti0.05BaCo4O7+δ, Y0.2Ti0.05Dy0.75BaCo4O7+δ, and Y0.15Zr0.1Dy0.75BaCo4O7+δ oxygen carriers, respectively. Random nucleation and nuclei growth A model is the most suitable for oxidation process. The A model and D are the most suitable for the reduction process. Regarding YBaCo4O7+δ, Y0.95Ti0.05BaCo4O7+δ, Y0.2Ti0.05Dy0.75BaCo4O7+δ, and Y0.15Zr0.1Dy0.75BaCo4O7+δ kinetic, oxygen transfer materials are rate-determined by nucleation and nuclei growth. For reduction kinetic, the gas diffusion stage could also become a dominant step.