The electrocardiogram is generally used clinically in diagnosing the heart diseases. Hence, it must be very accurate. Signals recorded are often contaminated with Power Lime 50 Hz noise and harmonics originating from power supplies, power mains and lights. The presence of noise cormpts the information content of these signals and can degrade the quality of subsequent data analysis. This electrical interference is notoriously difficult to remove without altering the original signal imbedded within the noise. The power line interference reduction in ECG records is a challenging problem which is still open for research. The power line signal, measured directly &om the transmission l i e may have amplitude, phase and frequency variations. This paper deals with designing 50 Hz Twin-T notch filter for elimmating the power line noise from ECG signal. i~b .L+llllr L h 3j % 3 1 3 1 1 ! , &I &Ip\ 4 4 ' &I S! 4 1 YJ j k hi, $ 9 0 .
In spite of many advantages of an asynchronous generator, its use in isolated systems has been very limited due to the difficulties involving in conholling the variation of its generated voltage and frequency due to variation of load current. This paper gives the possibility to minimize the variation of the output voltage and frequency. The technique utilize an algorithmis implemented using PLC devices. PLC has the resposibility of the system sequence control for output voltage and frequency. The system functions were analized and implemented in PLC based hardware and software. The control system was tested systematically in the laboratory and shows excellent performance.
Mode I1 fracture toughness of hybrid fiber reinforced concrete HFRC has been experimentally investigated. The effect of crack length to depth ratio, a\w, was studied. The mechanical properties of different hybrid fiber reinforced concretes were deteimined in an attempt to relate the parameters of concrete type to its fracture toughness. Three different fiber types (steel "S", glass "G" and polypropylene "PF"') were used. The volume fraction Vf was kept constant equal to 1.5% for all FRCs with different configurations. These configurations are steel fiber only with 1.5% Vf (SFRC), steel fiber with 1% VF in addition to glass fiber with 0.5% Vf (SGFRC), and steel fiber with 1% Vf in addition to polypropylene fiber with 0.5% Vf(SPPFRC). The crack length to depth ratio was equal to 0.3, 0.4 and 0.5 for fracture toughness specimens. The cement content was 450 kg/m3 for all mixes. The fracture toughness Kllc was determined according to fornula of Watkins model by using cracked cubes 150 X 150 X 150 mm. Results of the present workindicated that, the addition of short fibers slightly increase the compressive strength of FRC. The presence of fibers significantly increases 'the splitting tensile strength of FRC for different types of fibers. For Plain concrete Knc was not dependent on the value of dw, i.e. intrinsic property. On the other hand, The mode I1 fracture toughness (KIrc) for all FRCs mixes, decreases with the increase in the ratio alw due to the absence of fibers to connect the two surfaces of pre-crack.
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