Emerging engineering challenges in wind power electricity generation bond with stringent industrial requirements, have tendency to outline development and design process in the ready set go manner. ...From given predisposition one of the consequences may be highlighting of certain research area or even worse - deflection from the basic functional requirements in wind turbine drive train design. The paper presents a proposal of novel drive train technology - gear transmission unit with continual variation of transmission ratio which can provide direct synchronization to public electric grid, efficient energy conversion and wider operating range of wind turbine rotor. Beside mechanical, electronic and software system design, novel wind turbine configuration is also presented.
A new design of gear transmission unit with continual variation of gear transmission ratio, for application in wind turbines (WT), has been developed. By variation of transmission ratio the speed of ...output shaft is 1500 rpm, constant independently of the wind speed. The article contains the presentation of a testing rig and the testing procedure of this design. The testing rig is based on back-to-back connection and power circulation and the testing procedure on simulation of the WT service conditions. The objective of testing process is identification of gearbox operating features and behavior, gearbox reliability and durability.
Extreme powerful gear drives have a relatively elastic structure of housing components. The supports and the connections with the carrying structure are not rigid enough either, including this ...structure itself. The paper analyses the gear unit supporting bearings failure of bucket wheel excavators. The failure of BWE SchRs-1600 occured after a very short service life, in the form of progresive and catastrophic pitting. The presented analysis shows that this phenomenon appeared due to multiple synchronized influences which are a direct consequence of the structure elasticity, the reducer and output shaft masses eccentricity, the moment lever rigidity, and the bearing area local deformations. An improved design solution as well as the mentioned analyses are presented. Additionally, gear transmission units can operate properly in the resonance conditions but they cause very unfavorable effects on other components, such as the bearings. The article contains gear resonance identification and its influence on rapid failure of bearings and other gears of the SRs-1301 bucket wheel excavator. Thereafter follows the correction of design parameters of the critical gear pair in order to avoid its resonance and excitation of natural frequencies of gearbox housing.Original Abstract: Zupcasti prijenosnici velikih snaga imaju relativno elasticna kucista. Takoder oslonci i veze s nosivom konstrukcijom nisu dovoljno krute, ukljucujuci i samu strukturu prijenosnika. Clanak sadrzi analizu razaranja lezaja reduktora rotornih bagera. Kod rotomog bagera SchRs-1600, kvar se dogodio nakon vrlo kratkog rada u formi progresivnog i vrlo razarajuce rupicavosti (pitinga). Prikazana analiza ukazuje na to da se ovaj fenomen pojavio zbog visestrukih sinhroniziranih utjecaja koji su direktna posljedica elasticnosti strukture, ekscentricnosti reduktora i masa izlaznog vratila, krutosti momentne poluge i lokalnih deformacija u okolini lezaja. Poboljsano konstrukcijsko rjesenje skupa sa spomenutim analizama prikazani su u radu. Osim toga, zupcanici u zupcastim prijenosnicima mogu ispravno raditi u uvjetima rezonancije, ali oni izazivaju vrlo nepovoljne uvjete za rad drugih komponenata kao sto su lezaji. Clanak sadrzi identifikaciju rezonancije zupcanika kao i analizu njihovog utjecaja na ostecenja lezaja i drugih zupcanika, koja nastupaju vrlo brzo, kod rotornog bagera SRs-1301. Iza toga slijedi prikaz uskladivanja parametara konstrukcijskog rjesenja kriticnog zupcastog para kako bi se izbjegla njegova rezonancija i pobuda vlastitih frekvencija kucista.
Zupčasti prijenosnici velikih snaga imaju relativno elastična kućišta. Također oslonci i veze s nosivom konstrukcijom nisu dovoljno krute, uključujući i samu strukturu prijenosnika. Članak sadrži ...analizu razaranja ležaja reduktora rotornih bagera. Kod rotornog bagera SchRs-1600, kvar se dogodio nakon vrlo kratkog rada u formi progresivnog i vrlo razarajuće rupičavosti (pitinga). Prikazana analiza ukazuje na to da se ovaj fenomen pojavio zbog višestrukih sinhroniziranih utjecaja koji su direktna posljedica elastičnosti strukture, ekscentričnosti reduktora i masa izlaznog vratila, krutosti momentne poluge i lokalnih deformacija u okolini ležaja. Poboljšano konstrukcijsko rješenje skupa sa spomenutim analizama prikazani su u radu. Osim toga, zupčanici u zupčastim prijenosnicima mogu ispravno raditi u uvjetima rezonancije, ali oni izazivaju vrlo nepovoljne uvjete za rad drugih komponenata kao što su ležaji. Članak sadrži identifikaciju rezonancije zupčanika kao i analizu njihovog utjecaja na oštećenja ležaja i drugih zupčanika, koja nastupaju vrlo brzo, kod rotornog bagera SRs-1301. Iza toga slijedi prikaz usklađivanja parametara konstrukcijskog rješenja kritičnog zupčastog para kako bi se izbjegla njegova rezonancija i pobuda vlastitih frekvencija kućišta.
Introduction: Obesity is a growing health problem in economically developed countries. Abdominal fat is distributed in two large compartments: visceral fat is localized in the abdominal cavity ...(around the abdominal organs) and subcutaneous fat (between the skin and muscle layers of the abdominal wall). Ultrasonography is the most appropriate imaging method for estimating the amount of visceral and subcutaneous abdominal fat in obese patients. Aim: The aim is to assess the correlation between the amount of visceral and subcutaneous abdominal adipose tissue, estimated by ultrasound in obese individuals, and biochemical indicators of their glycolipid status. Material and Methods: Retrospective study included 183 adult obese patients (131 women and 52 men, mean age 42.6 ± 12.2, mean weight 123.4 ± 26.7 kg, mean BMI 43.5 ± 7.6kg/m2), in whom diameters of visceral (dVAFT) and subcutaneous abdominal fat (dSCAFT) were measured by ultrasonography. Following anthropometric parameters, height, weight, waist circumference (WC) and hip cimrcumference (HC) were also measured. Also, biochemical analysis of the concentration of glucose, insulin, HbA1c, triglycerides and cholesterol (parameters of the glycolipid status) was done. Correlation among these parameters was tested using Pearson's test of linear correlation (r). Results: Positive correlation was found between the dVAFT and all analyzed biochemical parameters of the glycolipid status (p < 0.001). The exceptions were total cholesterol (p = 0.158), negative correlation between the dSCAFT and concentrations of serum glucose, HbA1c and triglycerides (p < 0.01), dVAFT/dSCAFT index most strongly positively correlated with the glucose concentration (r = 0.534), HbA1c (r = 0.456) and triglyceride levels (r = 0.443). WC and WC/HC index significantly correlated with the concentration of all biochemical parameters of glycolipid status, except total cholesterol, but less strongly than dVAFT and dVAFT/dSCAFT index. Conclusion: Visceral and subcutaneous abdominal fat diameters were measured by ultrasound, and especially dVAFT/dSCAFT index, express stronger correlation with the biochemical parameters of glycolipid status, than the anthropometric parameters, in adult obese people.
Management of pancreatic pseudocysts - a single center experience Pavlovic, Ivana; Knezevic, Djordje; Bogdanovic, Marko ...
Pancreatology : official journal of the International Association of Pancreatology (IAP) ... et al.,
05/2013, Letnik:
13, Številka:
3
Journal Article
Recenzirano
Conclusion: We determined that percutaneous drainage is less favourable procedure with high failure rate in comparison with conventional surgery as it resulted in longer hospital stay, higher ...morbidity rates and higher overall incidence of complications.
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