In this study, the effect of welding heat input on microstructure and mechanical properties of dissimilar joints of API-X42 and API-B pipeline steels was investigated. Evaluation of the microstructures showed that increasing the welding heat input decreased acicular ferrite in weld metal microstructure, while amount of Widmanstatten ferrite, polygonal ferrite and grain boundary ferrite increased. Also, results of microhardness test showed that by increasing the heat input, hardness of weld metal and the heat affected zone decreased. Tensile test results showed that as the heat input increased, fracture transferred from base metal of API-B to the heat affected zone. Impact test results also showed that increasing the welding heat input could sharply drop the impact energy of the heat affected zone for both base metals due to extensive grain growth.

In recent years, the tendency for ransomware-based cyberattacks has increased dramatically. One of the defensive methods is the behavioral detection of the ransomware by system functions. Literature review and related studies and investigations in this field show that these researches are not optimum concerning the accuracy and speed of ransomware detection. Because all datasets used in these studies are limited in scope, they have shortcomings such as high false positive or false negative rates and even high indiscriminate rates. Another drawback of these schemes is the failure to expedite the debate on extortion ransom. Therefore, in this study, the first step is to generate an initial dataset with 126 attributes containing all types of ransomware families. Then, by performing 4-step experiments and tests and applying a feature selection algorithm, this initial set is processed and optimized and reduced to a dataset with 67 attributes without loss of detection precision. In the final step, by providing an optimal and so-called lightweight dataset, the best classification model for the detection of ransomware is obtained being capable of identifying ransomwares with an optimum precision rate of 95. 11 in 0. 21 seconds, a false positive rate of 0. 047 and a true positive rate of 0. 951 by using a random forest classification algorithm (using 10-part cross-validation method).

As we all know, corrosion of pipelines by hydrogen sulfide is the most worrying factor in the production and transport of oil and gas. In this work the corrosion behavior of API 5L X70MS and X70MO low carbon steels in hydrogen sulfide environments was investigated. Hydrogen induced cracking and sulfide stress cracking tests were carried out according to NACE TM0177 standard. After testing, blisters and cracks were observed only in X70MO steel, probably due to its lower grain refinement and banded microstructure. Internal cracks seem to be initiated in elongated MnS inclusions. Corrosion process was studied by obtaining potentiodynamic polarization curves, which were registered after open circuit potential measurements, at room temperature. Both steels showed general corrosion in NACE 177A solutions, but the corrosion rate values ​​in H2S-saturated solution were about an order of magnitude higher than those ones in deaerated solution. Hydrogen permeation w::as char::acterized in accordance with ASTM G148 standard. In deaerated H2SO4 solution, permeation measurements were similar for both steels. In H2S-saturated solution, X70 MO exhibited higher hydrogen oxidation current values ​​than X70 MS. H2S seems to promote the reduction of protons and increase the concentration of hydrogen atoms in the solution/steel interface, favoring the diffusion process. As X70MO has a coarse microstructure, it offers more pathways for hydrogen diffusion.

The effect of electromagnetic vibration on the microstructure and impact toughness of API-X70 steel weld metal was investigated. The welding was carried out by gas tungsten arc welding process and using filler metals including ER80S-G and ER309L. Electromagnetic vibration under voltages 0-30 volts concurrent with welding was applied. The microstructure of the base and weld metals using optical microscope and SEM was studied. The impact energy of weld metals at TR, 0° C and-20℃ using charpy impact test was measured. Microstructural investigations revealed that applying electromagnetic vibration have caused the finer and more uniform of Martensitic-Austenitic (MA) islands in the ER80S-G weld metal. The results showed that, due to electromagnetic vibration, the microstructure became finer and the average size of dendrites in the ER309L weld metal decreased from 18. 19 to 8. 01 μ m. . The impact test result, illustrated that the applied vibration cause improvement of impact energy of weld metals at different temperature (TR, 0° C and-20℃ ). It was found that with vibration under 30V, impact energy of ER80S-D weld metal in TR, 0° C and-20℃ was increased equal to 53, 29 and 36 percents, respectively. Besides for ER309L weld metal, the impact energy in TR and-20℃ was increased equal to 18 and 5 percents, respectively. (TR= Room Temperature).