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    Supracondylar process of the humerus
    (2002) Subasi M.; Kesemenli C.; Necmioglu S.; Kapukaya A.; Demirtas M.
    Four cases of supracondylar process of the humerus in three patients are presented. The main features of a supracondylar process as compared with an osteochondroma are reviewed. The three patients had pain and one had signs indicating median nerve compression. One had a supracondylar process together with an osteochondroma in the contralateral supracondylar region. One patient with a bilateral supracondylar process refused an operation. The other two patients underwent surgical treatment. The symptoms disappeared in the two patients who were operated.
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    Öğe
    Thyristor drive, of immersion electro-centrifugal pump for oil production
    (2002) Abdulrakhmanov K.; Redfern M.A.; Rustemov S.; Guneli S.S.; Demirtas M.
    Oil extraction pumps are essential for obtaining oil in many of the world's oil fields. Their operating environment presents several challenges for engineers and those responsible for designing the systems, their power supplies and the associated control systems. These units are typically located 2000 metres below the well head and are powered by a three-phase supply from the surface. The inaccessibility of the pump limits the opportunities for direct measurements of the operation of the pump and its motor. The paper considers the closed-loop control system for an immersed electro-centrifugal pump used for oil production. Optimal operation of the pump is achieved when the motor's input is equal to the discharge from the well. Dynamic control is performed by means of monitoring the motor's speed by changes in its EMF and the pumped oil pressure measured at the pump unit. This control scheme uses the 3rd harmonic EMF from the stator windings as carried by the power cable. This power cable is also used to carry a high frequency signal obtained from the pressure transducer system. The paper includes a steady state analysis of the system and presents analysis for calculating key parameters for defining the system's operating characteristics.