The paper deals with the rotor vibration in journal bearings to prepare a model for verifying the rotor vibration active control. The rotor is maintained in equilibrium position by forces generated in oil film. Bearing forces can be modelled as a spring and damper system. The main goal of the simulation study is to verify the model principle and to estimate parameters by comparing simulation results with experimental data, namely the instability of motion. Test stand with rotor supported in two journal bearings was designed for these purposes. The stand will be equipped with four piezoactuators enabling excitation of bearings by practically arbitrary dynamic force. Theoretical analysis of the influence of external excitation on rotor behaviour was carried out. Up to now the study shows that simple kinematic excitation is effective for reducing rotor excursion while passing critical speeds. To suppress self-exciting vibration of the rotor it is necessary to look for more sophisticated solution. and Obsahuje seznam literatury
New type of aerodynamic tilting pad journal bearing was designed and successfully tested in several applications, one of which was power gyroscope support. Bearing design combines advantages of foil bearings, i.e. additional damping achieved by squeezing out gas film and friction of elastic elements on bearing casing surface, with qualities of classical tilting pad bearings, consisting in defined geometry of bearing gap and excellent stability. Theoretical solution of bearing characteristic calculation is shortly described, consisting in numerical solution of gas flow in narrow gap. Some computed data and results of experiments with rotors operated up to 180.000 rpm are presented too. and Obsahuje seznam literatury
The authors demonstrate the possibility of improving surgical results by the reduction of perioperative bleeding in thoracic surgery associated with extended resection procedures. We focused on patients in whom the expected perioperative blood loss was greater than 500 ml. The first group consisted of patients with lung cancer stage III A after neoadjuvant chemotherapy had been indicated to extend the resection procedure. The second group consisted of patients with chest wall and mediastinum tumors of various etiologies. The third group consisted of patients with post-inflammatory thoracic complications in whom combined decortication and pleurectomy was necessary. By the using the local hemostyptic Traumastem TAF on the basis of oxidized cellulose, it is possible to minimize the perioperative blood loss, thus sparing the blood derivative requirement and enabling surgeons to provide the desired treatment even to high-risk patients., Petr Habal, Nedal Omran, Jiří Manďák, Jiří Šimek, Milan Štětina, and Literatura 16
Paper deals with subject of identification of aerostatic journal bearings dynamic properties with use of Rotor Kit Bently Nevada superstructure. Different bearing types were experimentally investigated and their static and dynamic characteristics were identified. Various methods of identification were used and spectral and modal properties of the system were calculated. Computer program was revised on the basis of experimental data. The influence of non-diagonal stiffness and damping elements was investigated by numeric stimulation. and Obsahuje seznam literatury
Vzdálené metastázy maligních tumorů do oblasti obličeje jsou vzácné. Vyskytují se jak v měkkých tkáních ústní dutiny a obličeje, tak ve skeletu čelistí a jejich diagnostika nemusí být vždy snadná. Při plánování terapeutických postupů je nutné brát v úvahu celkový stav pacienta, prognózu a stupeň generalizace nádorového onemocnění. Na příkladech tří pacientů autoři prezentují vlastní zkušenosti s diagnostikou a terapií orálních metastáz zhoubných nádorů extraorální primární lokalizace. Práce je doplněna souhrnem dostupných informací o incidenci metastatických zhoubných nádorů v orofaciální oblasti., Distant metastasis of malignant tumors in the facial area are rare. They occur both in the soft tissues of the oral cavity and face and skeletal jaw bones and their diagnosis is not always easy. In planning therapeutic procedures, one must take into account the patient‘s general health, prognosis and degree of cancer generalization. The authors present their own experience in the diagnosis and therapy of three cases of oral cancer metastasis with extraoral primary localisation. The histories are accompanied by a summary of available information on the incidence of metastatic malignant tumors in the orofacial region., Štefan Juhász, Richard Pink, Jiří Šimek, Petr Tvrdý, and Literatura