The effect of NaF and NaNO3 based degasser on mechanical properties of Al-Si 12% casting has been investigated. The quality of Al-Si casting, especially in mechanical properties, is important in some applications. However, the existence of gas porosity, which is formed due to the high solubility of H2 at melt temperature in casting process, reduces mechanical propertis of Al-Si 12% casting product. In this research, we used NaF and NaNO3 as degasser as an addition in casting process. The experiments were conducted at pouring temperature of 660°C, 680°C, 700°C and 720°C. The mechanical properties (which are determined by tensile test, hardness test and impact test) with and without degasser were measured and compared. We found that in all pouring temperature, the addition of degasser will improve all of mecahnical properties measured. In addition we found that the increase of tensile strength was optimum at pouring temperature of 720°C at 25,5 % of increase, hardness was optimum at pouring temperature of 720°C at 33,3 % of increase and impact strength was optimum at pouring temperature of 720°C at 25 % of increase. The improvement of mechanical properties is due to the role of NaF and NaNO3 by binding H2 gases which is formed in melting process. This H2 binding was shown in microstructure observation which shows that the porosity of casting product visually decreased.
A fractured flanged thermowell was received for analysis. The fracture was located at the root of ''U'' insertion/immersion length which was welded to the flange. The failure of flanged thermowell was attributed to the vortex-induced fatigue. The failure was initiated by the weld failure to withstand the fluctuating load resulted from vortex after years of service. This weld failure then created stress raisers, as evidenced by the ratchet marks and river marks near the outer surface.
In a video call there are several components, such as IP phone or softphone, CODEC, and server. Selection of softphone and CODEC is a consideration in building a video communication network because it will affect the quality of video call. This research compare the quality of video calls based on softphone application and CODEC combination. The quality measured by QoS, PSNR, and MOS parameters.Softphone applications examined in this research are Blink, Zoiper, MicroSIP, PortGo, Linphone, and X-Lite. CODEC examined in this research are H.264, VP8, H.263+, and H.263. Each softphone application will be combined with a CODEC that is native to the softphone. There are nine combinations of softphone application and CODEC.Based on the research results, CODEC H.264 has the best performance when paired with the Blink softphone application. CODEC VP8 has the best performance when paired with the Zoiper softphone application. The H.263+ CODEC has the best performance when paired with the PortGo softphone application. The H.263 CODEC and X-Lite softphone applications have the worst test results but still get “good” grades when tested using QoS, PSNR, and MOS parameters.
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