34 research outputs found
A model-based prediction of balancing behavior of rotors above the speed range in available balancing systems
No full textRotor balancing is probably the most discussed topic in the entire literature about rotor dynamics. It would therefore seem that, from the point of view of theory, this is a problem of little interest, however, balancing is very relevant in the industrial practice and sometimes there are very particular cases that cannot be addressed and solved by traditional methods. Moreover, many papers deal with only simulated results or with small-scale tests-rigs, which can hardly reproduce the behavior of real rotors. The case described in this paper is just one of these and presents what could be defined as “predicting the effect of balancing” at rotational speeds that are higher than those possible on balancing machines. Rotordynamics modeling, identification techniques developed by the authors and the available vibration measurements allow the simulation of the behavior, i.e. the vibrations, of the considered turbine rotor on the balancing machine,even at rotational speeds higher than those are possible to be reached, but that correspond to the trip speed in the plant
A Navigation Interface Based on Head Tracking by Accelerometers
No full textThis work presents a novel user interface for navigation in virtual environments and remote control of devices. The proposed system is head-mounted, allowing for the control of up to six degrees of freedom while leaving the user with free hands. The device is composed of six linear accelerometers arranged on a couple of glasses and a specific embedded controller that allows for the measuring of glass acceleration information. This is then translated in motion control information for navigation in virtual environments and/or as other devices input. The specific algorithms to integrate the motion acceleration cues sensed from the glasses while filtering the drifting errors and effect related to head rotations are presented herein
Full-scale vibration testing of nozzle guide vanes
No full textAn increasing number of turboexpanders are equipped with Nozzle Guide Vane (NGV) as the first stator stage. By varying the throat area of the first stator vane the NGV enables an additional control methodology to the line-up power output allowing higher operational flexibility and higher efficiency at partial load and partial speed. The design of this component might become critical for enabling high expander availability considering its exposure to high temperature, thermal loading, and fluid induced vibrations. This is especially true also considering that the vibration frequencies of this sub-assembly are influenced by internal clearances and by the value of the friction coefficient, which leaves a relevant margin of error when using numerical methods (such as FEM) for predicting the actual structural behavior of this component. In this paper, the design of a full-scale test bench for the determination of both friction coefficients and modal behavior of a nozzle guide vane geometry is described. The bench enables us to simulate the pre-load due to aerodynamic forces on the NGV airfoil simulating the actual working conditions of bushes and bearings
Parent's acquaintance with curriculum reform
No full textThis thesis is of a theoretical nature: it does not include any field research. It includes a proposal for an elementary school brochure-guide for parents in Czech Republic, created by the author of this thesis. The thesis summarizes findings on the educational curriculum reform in the Czech Republic, which took place in 2007, and analyses ways in which parents were informed. The text focuses first on the reform itself, its objectives and its basic features. It then analyses the relationship between family and school, stating that parents as a group are of major importance for the successful implementation of the reform. It is therefore crucial to properly understand this group. In connection with the reform and its importance for parents, the text deals with how the informational campaign was conceived in the Czech Republic and in the UK. The 'Guide for Parents of English pupils aged 5 to 7 years' is then described as a source of ideas. Based on this, a proposal for a brochure-guide was created to be used as informational material for parents in the Czech Republic
Robotic versus laparoscopic right colectomy with intracorporeal anastomosis: a multicenter comparative analysis on short-term outcomes
No full textIn literature, most of the comparative studies of robotic (RRC) versus laparoscopic (LRC) right colectomy are biased by the type of the anastomotic technique adopted. With this study, we aim to understand whether there is a role for robotics in performing right colectomies, comparing RRC versus LRC, both performed with intracorporeal anastomosis
The use of intra-abdominal drain in minimally invasive right colectomy: a propensity score matched analysis on postoperative outcomes
No full textPURPOSE: No evidences supporting or not the use of intra-abdominal drain (AD) in minimally invasive right colectomies have been published. This study aims to assess the outcomes on its use after robotic or laparoscopic right colectomies. METHODS: This is a multicenter propensity score matched study including patients who underwent minimally invasive right colectomy with (AD group) or without (no-AD group) the use of AD between February 1, 2007, and January 31, 2018. AD patients were matched to no-AD patients in a 1:1 ratio. Main outcomes were postoperative morbidity and mortality and anastomotic leak. RESULTS: A total of 653 patients were included. Of 149 (22.8%) no-AD patients, 124 could be matched. The rate of postoperative complications (AD n = 26, 21% vs. no-AD n = 26, 21%; p = 1.000), mortality (AD n = 2, 1.6% vs. no-AD n = 1, 0.8%; p = 1.000), anastomotic leak (AD n = 2, 1.6% vs. no-AD n = 5, 4.0%; p = 0.453), and wound infection (AD n = 9, 7.3% vs. no-AD n = 6, 4.8%; p = 0.581) did not significantly differ between the groups. Time to oral feeding was significantly shorter in the no-AD group [2 (1-3) vs. 3 (2-3), p = 0.0001]. The median length of hospital stay was 8 (IQR 7-9) in the AD group while it was 6 (IQR 5-9) in the no-AD group (p = 0.010). CONCLUSIONS: In conclusion, the use of AD after minimally invasive right colectomies has no influence on postoperative morbidity and mortality rate
Total Electron Content Measurements at Gauhati Using 140 MHz ATS-6 Transmissions
No full text241-244The amplitude and phase of 140 MHz transmissions from geostationary satellite ATS-6 (0oN, 35°E) have been recorded at Gauhati (26·15°N; 91·75°E) for the period Nov. 1975 to Aug. 1976. The calibration technique for geostationary satellite Faraday rotation measurements suggested by Checcacci and Giorgeo [Checcacci, P. F. & Giorgeo, M, T., J. almos.terr. Phys. 37 (1976),119] has been improved and generalized, It is then utilized to remove the nπ ambiguity in Faraday rotation values and also to estimate the correct value of diurnal minimum Faraday rotation angle so that the recorded Faraday rotation values can be converted into electron content values. Typical diurnal variation curves have been obtained for all the months except for equinoxes when the satellite transmission was off very often due to ecliptic conditions and hence no complete diurnal curves could be obtained for these months, It has been found that though December and January behave like typical winter months, the month of November is more like an equinoctial month. Similarly, though June and July behave like typical summer months the month of May is more or less similar to equinoxes. The characteristic features of the diurnal and seasonal behaviour of the electron content have been discussed
Space‐variant transfer functions for the characterization of inhomogeneous scattering media
No full text
