Journal of Engineering and Technological Sciences
Not a member yet
888 research outputs found
Sort by
Pitting Corrosion in AA7075 Friction Stir Welds on Minor Additions of Silver
Get PDFAA7075 is extensively used in aerospace, defense, automotive applications because of its high strength to weight ratio. Issues related to fusion welding and corrosion resistance are key problems associated with these alloys. Friction stir welding is an alternative welding technique that overcomes problems associated with fusion welding. In the present investigation, preliminary studies were done on pitting corrosion behavior of AA7075 friction stir welds by adding silver along the weld joint line. Silver paste was applied along the longitudinal direction of AA7075-T6 rolled plates of 6-mm thickness and cured at 130 °C for 30 seconds. Weld joints were prepared at two different tools rotational speeds, i.e., 750 rpm and 1000 rpm, while keeping other parameters fixed. Welded joints were cut as per the required sizes to study the hardness, microstructure, and pitting corrosion resistance in various regions. It was observed that the hardness was not much affected, but pitting corrosion resistance substantially improved by trace addition of silver. In the stir zone and the thermo-mechanically affected zone, onion ring type marks were observed. Grain refinement in the stirred zone (SZ) was higher at 750 rpm compared to 1000 rpm. The increased hardness in the welds was due to grain refinement. All the observed results were correlated with microstructural features as evidenced by optical microscopy
Data Driven Building Electricity Consumption Model Using Support Vector Regression
Get PDFEvery building has certain electricity consumption patterns that depend on its usage. Building electricity budget planning requires a consumption forecast to determine the baseline electricity load and to support energy management decisions. In this study, an algorithm to model building electricity consumption was developed. The algorithm is based on the support vector regression (SVR) method. Data of electricity consumption from the past five years from a selected building object in ITB campus were used. The dataset unexpectedly exhibited a large number of anomalous points. Therefore, a tolerance limit of hourly average energy consumption was defined to obtain good quality training data. Various tolerance limits were investigated, that is 15% (Type 1), 30% (Type 2), and 0% (Type 0). The optimal model was selected based on the criteria of mean absolute percentage error (MAPE) < 20% and root mean square error (RMSE) < 10 kWh. Type 1 data was selected based on its performance compared to the other two. In a real implementation, the model yielded a MAPE value of 14.79% and an RMSE value of 7.48 kWh when predicting weekly electricity consumption. Therefore, the Type 1 data-based model could satisfactorily forecast building electricity consumption
LSCF-CuO as Promising Cathode for IT SOFC
Get PDFInfiltration of copper oxide towards LSCF was done in order to enhance cathode performance due to superior properties, including high electrical conductivity and high catalytic activity for the oxygen reduction reaction. Samples were synthesized at different temperatures using the sol-gel route. The TGA results showed that LSCF achieved complete perovskite formation when calcined above 600 °C and DTA showed the formation of lattice oxygen at 550 °C. XRD analysis showed no shifted peaks and nano size levels were achieved when samples were calcined at 700 °C and 800 °C. SEM and BET showed similar analysis patterns, where the particle size increased as the calcining temperature was increased. EIS analysis further verified that the polarization resistance of the sample calcined at 700 °C was as small as 0.161 Ω, compared to 1.524 Ω with a calcination temperature of 800 °C. The activation energy of LSCF-CuO was found to be 122.2 kJ/mol, which is much lower than for conventional LSCF
Acquaintance Management Algorithm Based on the Multi-Class Risk-Cost Analysis for Collaborative Intrusion Detection Network
Get PDFThe collaborative intrusion detection network (CIDN) framework provides collaboration capability among intrusion detection systems (IDS). Collaboration selection is done by an acquaintance management algorithm. A recent study developed an effective acquaintance management algorithm by the use of binary risk analysis and greedy-selection-sort based methods. However, most algorithms do not pay attention to the possibility of wrong responses in multi-botnet attacks. The greedy-based acquaintance management algorithm also leads to a poor acquaintance selection processing time when there is a high number of IDS candidates. The growing number of advanced distributed denial of service (DDoS) attacks make acquaintance management potentially end up with an unreliable CIDN acquaintance list, resulting in low decision accuracy. This paper proposes an acquaintance management algorithm based on multi-class risk-cost analysis and merge-sort selection methods. The algorithm implements merge risk-ordered selection to reduce computation complexity. The simulation result showed the reliability of CIDN in reducing the acquaintance selection processing time decreased and increasing the decision accuracy
Experimental Studies on Mechanical Properties of Carbon Nanotube Reinforced Aluminum 7075 Composite Material
Get PDFIn the present work multiwalled carbon nanotubes were added as reinforcement to aluminum 7075 matrix at 0.5%, 0.75% and 1.25% by weight proportion through stir casting technique. The mechanical properties of the produced composite were studied. The composite has considerably good tensile and wear resistance properties and hence finds its best suited application in aircraft frame and wings structures. Microstructure analysis through SEM showed a uniform distribution of the reinforcement material in the matrix. XRD graphs were taken at selected points during microscopic studies to determine the chemical composition of the matrix alloy, the reinforcement and the composite. The experimental results showed that 1.25% reinforcement in the composite material exhibited a tensile strength of 560 N/mm2 and a compression strength of 649.6 N/mm2 as the highest among the compositions. Thus, the reinforcement addition at 1.25% improved the tensile and compression strength of the composite material