Current Issue : January - March Volume : 2020 Issue Number : 1 Articles : 5 Articles
Microwave-assisted pyrolysis is a promising thermochemical technique to convert waste\npolymers and biomass into raw chemicals and fuels. However, this process involves several\nissues related to the interactions between materials and microwaves. Consequently, the control\nof temperature during microwave-assisted pyrolysis is a hard task both for measurement and\nuniformity during the overall pyrolytic run. In this review, we introduce some of the main theoretical\naspects of the microwavesâ??materials interactions alongside the issues related to microwave pyrolytic\nprocessability of materials....
As a derivative product of bio-glycerol, this study first uses solketal as a combustion improver\nfor enhancing diesel engine characteristics. The emulsions of nanometer- and micrometer-sized\ndroplets of solketal, which disperse evenly in the ultra-low sulfur diesel (ULSD), are formed by the\neffects of microwave irradiation. The performance of diesel engine fueled with the nanoemulsion of\nULSD with scattered solketal droplets is analyzed and compared to that with the microemulsion.\nThe experimental results show that the nanoemulsions can form when over 15 wt. % surfactant\nmixtures of Span 80 and Tween 80 and less than 5 wt. % solketal are mixed and emulsified with the\nremaining ULSD content, which acts as the continuous phase of the emulsions. The nanoemulsions are\nobserved to have significantly lower brake-specific fuel consumption (bsfc) and higher fuel conversion\nefficiency and exhaust gas temperature than those of the microemulsions and the neat ULSD. However,\nthe bsfc of the nanoemulsions increases with greater engine speed and gradually approaches those\nof the latter two test fuels. In addition, the dispersed solketal droplet sizes are mostly concentrated\naround 127nmwith peak intensity of 12.65% in the nanoemulsions. The microwave-assisted formation\nused in this study is found to successfully produce the nanoemulsions in which all of the dispersed\ndroplet sizes are much smaller than 1000 nm....
This manuscript focuses on the analysis of a critical height of radio altimeters that can help for\nthe development of new types of aeronautical radio altimeters with increased accuracy in measuring\nlow altitudes. Altitude measurement accuracy is connected with a form of processing the difference\nsignal of a radio altimeter, which carries information on the measured altitude. The definition of\nthe altitude measurement accuracy is closely linked to the value of a critical height. Modern radio\naltimeters with digital processing of a difference signal could shift the limit of accuracy towards better\nvalues when the basics of the determination of critical height are thoroughly known. The theory\nresults from the analysis and simulation of dynamic formation and the dissolution of the so-called\nstable and unstable height pulses, which define the range of the critical height and are presented\nin the paper. The theory is supported by a new method of derivation of the basic equation of a\nradio altimeter based on a critical height. The article supports the new theory of radio altimeters\nwith the ultra-wide frequency deviation that lead to the increase the accuracy of a low altitude\nmeasurement. Complex mathematical analysis of the dynamic formation of critical height and a\ncomputer simulation of its course supported by the new form of the derivation of the basic equation\nof radio altimeter guarantee the correctness of the new findings of the systematic creation of unstable\nheight pulses and the influence of their number on the altitude measurement accuracy. Application\nof the presented findings to the aviation practice will contribute to increasing the accuracy of the low\naltitude measurement from an aircraft during its landing and to increasing air traffic safety....
The paper presents the concept, implementation, and test operation of a modernized solar\nradio spectrograph for an investigation of the solar emission and solar bursts in radio frequency\nbands. Besides having a strong diagnostic significance for studying the flare energy release, the solar\nradio bursts can also cause strong interference for radio communication and navigation systems. The\ncurrent spectrograph for the Ondrejov observatory (Astronomical Institute of Czech Academy of\nSciences) was modernized by using a direct-conversion receiver connected to a field-programmable\ngate array (FPGA) for the fast Fourier transform (FFT) spectrum estimation and put into the test\noperation. The higher time and frequency resolution and lower noise in comparison with the existing\nanalog instrument were reached by the implementation of the latest optimal signal processing\nmethods. To reduce the costs for such modernization, the operating frequency range was divided\ninto four sub-bands of bandwidth 250 MHz, which brings another benefit of greater scalability. The\nfirst observations obtained by the new spectrograph and their comparison with the analog device are\npresented in the paper with future steps to put the spectrograph into the regular operation....
Hepatocellular carcinoma (HCC) is the most common primary cancer of the liver. Hepatectomy and liver transplantation (LT) are\nregarded as the radical treatment, but great majority of patients are already in advanced stage on the first diagnosis and lose the\nsurgery opportunity. Multifarious image-guided interventional therapies, termed as locoregional ablations, are recommended by\nvarious HCC guidelines for the clinical practice. Transarterial chemoembolization (TACE) is firstly recommended for\nintermediate-stage (Barcelona Clinic Liver Cancer (BCLC) B class) HCC but has lower necrosis rates. Radiofrequency ablation\n(RFA) is effective in treating HCCs smaller than 3 cm in size. Microwave ablation (MWA) can ablate larger tumor within a\nshorter time. Combination of TACE with RFA or MWA is effective and promising in treating larger HCC lesions but needs\nmore clinical data to confirm its long-term outcome. The combination of TACE and RFA or MWA against hepatocellular\ncarcinoma needs more clinical data for a better strategy. The characters and advantages of TACE, RFA, MWA, and TACE\ncombined with RFA or MWA are reviewed to provide physician a better background on decision....
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