Escola Politécnica

PRODUCTION OF SILICA GEL FROM RESIDUAL RICE HUSK ASH

This paper presents a study on the production of silica gel in hydrothermal process using residual rice husk ash. Measurements of the chemical composition, X-ray diffraction, infrared spectroscopy, particle size distribution, and pozzolanic activity were carried out in order to characterize the obtained material, and the optimal silica gel was selected for use as a mineral additive in cement pastes. The compressive strengths were determined for cement pastes containing silica gel (0.0, 2.5 or 5% by mass) in different times. The results indicate that the mixtures containing silica gel showed improved mechanical behavior over all time periods evaluated.

Estudo do nitrogênio na combustão do gás natural

Nitrogen content in natural gas was studied in experimental and computational investigations to identify its influence on the emission level of exhaust gases from combustion facilities. Changes in natural gas composition with different N2 concentrations may result from introducing a new source gas into the system. An industrial burner fired at 75 kW, housed in a laboratory-scale furnace, was employed for runs where the natural gas/N2 proportion was varied. The exhaust and in-furnace measurements of temperature and gas concentrations were performed for different combustion scenarios, varying N2 content from 1-10 %v. Results have shown that the contamination of natural gas with nitrogen reduced the peak flame temperature, the concentration of unstable species, the NOX emission level and the heat transfer rate to the furnace walls, resulting from the recombination reactions.

A utilização de etanol em célula a combustível de óxido sólido

This work reports a review on the status and technical feasibility of the application of ethanol as fuel for Solid Oxide Fuel Cells (SOFC), presenting both external reform and cell with direct utilization of ethanol. Based on this survey, both experimental results and mathematical modeling indicated the technical feasibility of power generation by ethanol SOFC, with cell units producing 450 mW/cm2, sufficient for scale up to large stationary plants. The quantitative assessments in the literature show this field to be promising for researchers and private sector investment as well being a strategic technology for government policy in the short and long term.

HYPERVISOR AGNOSTIC WORKLOAD CHARACTERIZATION OF VIRTUAL MACHINES

Workload characterization is an important feature in a cloud environment. Using a fast and accurate characterization cloud providers can allocate virtual machines in physical hosts that best fit a specific workload and improve the overall performance without new investments. Current strategies of workload characterization are based on complex algorithms that are difficult to apply in a cloud environment with thousands of virtual machines running. Other strategies to characterize virtual machines rely on several changes in a hypervisor, or virtual machine layer, and are hypervisordependent. This paper presents a hypervisor agnostic characterization methodology that uses standard metrics of Processor and Memory utilization, available in SNMP. Collected data are normalized and applied to a low computational cost decision tree, that is able to characterize a virtual machine in a customizable time window. As evaluation, some tests were performed in different hypervisors (KVM, Xen and VMWare) running spec benchmark and in real workloads, such as Hadoop Cluster in Rackspace and a production Web Server running in a VMWare Farm. Results showed that our methodology is able to infer a very accurate characterization.

Morphological and Electrical Characterization of Ti and Zr Sputter-Deposited Thin Films

E. F. Chinaglia*,**, and I. C. Oppenheim* *Department of Metallurgy and Materials Engineering, Escola Politecnica, Universidade de Sao Paulo, Av. Prof. Mello Moraes, 2463, Sao Paulo, SP, 05508-900, Brasil. **Shimadzu do Brasil Comercio Ltda., Av. Marques de Sao Vicente, 1771, Sao Paulo-SP, 01139-003, Brasil. e-mail: tatachi@usp.br Keywords: resistivity, surface morphology, thin films, titanium, zirconium, sputtering, atomic force microscopy, reflection coefficient, Mayadas-Shazkes Thin film morphology and electrical resistivity play an important role in modern technologies. In particular, subcomponents fabricated by Ti play an increasing role in microelectronic device technology as well as in the biomedical area [1-2]. Here the influence of substrate temperature (during deposition) and film thickness on the surface morphology and electrical resistivity of polycrystalline Ti and Zr thin films have been investigated. The well established Matthiessen’s rule, originally suggested for bulk metals, is also valid for thin metal films [3]. The rule states that the various electron scattering processes that contribute to the total electrical resistivity (ρ) of a metallic thin film do so independently and additively; i.e., ρ = ρ