Investigation of the load and service conditions influence conditions influence on the cardan coupling operational capacity

Генерално посматрано, сви машински системи се састоје од погонске и радне групе, односно погонске и радне машине. Спој ових машина се остварује посебним склоповима, машинским елементима – спојницама. Њихова основна функција је преношење оптерећења и кретања са погонске на радну машину. Познато је да су спојеви најчешће најслабија карика у сваком машинском систему. Сагласно великом скупу различитих радних и погонских машина, са различитим радним перформансама, развијен је велики број различитих спојница. Међутим, код транспортних средстава и других машина, услови рада налажу различите међусобне положаје погонске и радне машине. Име и појам посебне врста спојница везано је за пионире у конструкцији ових спојница, славног италијанског научника Ђеролама Кардана (Gerolamo Cardano, 1501-1576) и Роберта Хука (Robert Hooke, 1635-1703). Конструкциона решења ових спојница пролазила су кроз различите фазе развоја. Динамика развоја конструкционих решења ових спојница приказане је у посебном Поглављу 3 овe дисертације. Карданове спојнице (карданска вратила) су посебна врста механизама за преношење обртног момента, односно снаге, који спајају вратила чије се осе налазе просторно под извесним сталним или у току рада променљивим углом, дозвољавајући, при томе, у току времена релативно померање. Ово померање може бити угаоно и транслаторно. Главни показатељи радне способности карданових спојница је њихов радни век и степен поузданости. Највећи утицај на ове показатеље раднe способности има карактер расподеле линијског оптерећења код спрегнутих делова Карданове спојнице. У циљу расветљавања феномена расподеле линијског оптерећења и сагледавања степена компатибилности између геометријских карактеристика спрегнутих делова и расподела линијских оптерећења, у дисертацији су формирани аналинтички и нумерички модели под одговарајућим предпоставкама.general, all mechanical systems consist of drive and driven groups, or driving and driven machines. The connection of these machines is achieved by special joints, machine elements - couplings. It is known that these joints are often the weakest link in any mechanical system. Pursuant to a large set of different drive and driven machines with different operating performance, a large number of different coupling types were developed. However, а working conditions of transport vehicles and other machinery require different mutual positions of the driving and operating machinery. The name and concept of one type of couplings is related to the pioneers in the design of these joints, the famous Italian scientist Gerolamo Cardano (1501-1576) and Robert Hooke (1635-1703). The designs of these couplings are passed through various stages of development. The innovative designs development dynamics of these couplings are shown in a separate chapter 3 of this study. Cardan joints (cardan shafts) have a large range of applications in mechanical engineering because of the capability of transferring the load and motion from one shaft to another with different joint angle allowing, thereby, over time relative movement. This movement can be angular and translational. The main indicators of functional ability of cardan coupling are their service life and reliability. The greatest influence on these indicators of functional ability has the character of the linear load distribution on cardan joints rolling parts. In order to shed some more light to the phenomena of linear load distribution and correlation between the geometric characteristics of rolling elements and the distribution of the linear load, analytical and numerical models under appropriate assumptions are established in this study. The obtained results shows, that with the standard (the existing) geometry of rolling parts, the engagement of points in root of Cardan cross jurnal in the load transfer is negligible due to very uneven linear load distribution. This unfavorable distribution of the linear load can be reduced with an appropriate combination of geometrical parameters of cardan cross rolling parts. Greater improvement of linear load distribution, ordering the appropriate shape reconstruction of cardan cross rolling parts

GENETIC AND PHENOTYPIC TRENDS FOR UDDER TRAITS AND ANGULARITY OF HOLSTEIN FRIESIAN COWS

The present research aimed to investigate the genetic trends for udder traits (fore udder attachment; rear udder height; udder depth; front teat placement; rear teat placement; front teat length and rear teat length) and angularity of Holstein Friesian cows in Serbia. A multi-trait animal model was used to estimate genetic parameters, through REML procedures. In the study 10403 first-lactation cows Holstein type from 12 different regions in Serbia were included. The cows were daughters of 221 Holstein Friesian sires. The age at first calving was from 19 to 44 months, and there were 10 stages of lactation. Udder type traits and angularity were classified by 24 classifiers on a linear scale of 1 to 9. Udder type traits had heritability estimates ranging from 0.03 for rear teat placement to 0.12 for fore udder attachment, and angularity had heritability 0.10. Genetic trend for angularity of Holstein Friesian cows in Serbia shows that ribs are becoming less angular and extremely rounded, while genetic trends for udder traits show that teat lengths are becoming longer and inside of quarter, and udder is shallow. The genetic trend for fore udder attachment indicates there is indirect selection for weaker udders. © 2022, Pakistan Agricultural Scientists Forum. All rights reserved

Effects of Flue Gas Recirculation on NOx Emissions from Gas-Fired Utility Boilers

Gas-fired utility boilers are most common in the district heating system in the city of Belgrade. Thus, they are an important stationary source of NOx emissions, which are particularly harmful for people and environment. In this paper the effectiveness of the flue gas recirculation (FGR) system that is applied to reduce NOx emissions of the utility hot water and steam boilers in district heating plant is experimentally investigated. Two types of systems are analysed; the first with the application of flue gas recirculation fan at hot water boilers; and the second without the application of flue gas recirculation fan at steam boilers. In both cases the rate of flue gas recirculation was 10%. The results of measurements showed that applied FGR systems efficiently reduced NOx emissions from utility boilers by 20 to 50% and below the reference values defined by legislative regulations. Emissions are higher at steam boiler which is expected because of the higher flue gas temperature at boiler furnace. Since the measured values for hot water boilers are close to the reference values, it was concluded that there is a potential for further improvements by increasing the flue gas recirculation rate

Analysis of accidents and serious incidents in aviation using Microsoft Power BI tools

Safety is a priority in aviation and for all aviation entities, including civil aviation authorities, operators, air traffic control service providers and airports. With the air traffic volume increase, there is a growth in the aviation system efficiency and therefore it is necessary to maintain a high level of safety. Practical processing of the operational data includes the representation and analysis of accidents and incidents in aviation over the certain period. The data presented in the paper are based on the location of the safety event, flight phase, aircraft type, accident frequency rate and other possible factors that can affect aviation safety. The main goal of analyzing the operational data is to raise safety awareness, as well as to maintaining safety risks on satisfactory level including safety risks mitigation measures

Novel probability model of a bird – wind turbine collision

ICREPS 13 : The second International conference of renewable electrical power sources; Oct 16-18, 2013, Belgrad

Cost-effectiveness of pneumococcal conjugate vaccination in Croatia.

OBJECTIVE: Pneumococcus is a known cause of meningitis, pneumonia, sepsis, and acute otitis media in children and adults globally. Two new vaccines for children have the potential to prevent illness, disability, and death, but these vaccines are expensive. The Croatian Ministry of Health has considered introducing the vaccine in the past, but requires economic evidence to ensure that the limited funds available for health care will be used in the most effective way. METHODOLOGY: Croatia appointed a multidisciplinary team of experts to evaluate the cost-effectiveness of introducing pneumococcal conjugate vaccination (PCV) into the national routine child immunization program. Both 10-valent and 13-valent PCV (PCV10 and PCV13) were compared to a scenario assuming no vaccination. The TRIVAC decision-support model was used to estimate cost-effectiveness over the period 2014-2033. We used national evidence on demographics, pneumococcal disease incidence and mortality, the age distribution of disease in children, health service utilization, vaccine coverage, vaccine timeliness, and serotype coverage. Vaccine effectiveness was based on evidence from the scientific literature. Detailed health care costs were not available from the Croatian Institute for Health Insurance at the time of the analysis so assumptions and World Health Organization (WHO) estimates for Croatia were used. We assumed a three-dose primary vaccination schedule, and an initial price of US$30 per dose for PCV10 and US$ 35 per dose for PCV13. We ran univariate sensitivity analyses and multivariate scenario analyses. RESULTS: Either vaccine is estimated to prevent approximately 100 hospital admissions and one death each year in children younger than five in Croatia. Compared to no vaccine, the discounted cost-effectiveness of either vaccine is estimated to be around US$69,000-77,000 per disability-adjusted life-years (DALYs) averted over the period 2014-2033 (from the government or societal perspective). Only two alternative scenarios were borderline cost-effective (US$ per DALY averted less than 3×GDP per capita of approximately US$40,000). The first was a scenario based primarily on the WHO 2008 pneumococcal disease burden estimates for Croatia. The second was a scenario that assumed a fairly dramatic drop in the price of the vaccine over the period. Both vaccines would need to be priced at approximately US$ 20 per dose or less to be considered cost-effective under base-case assumptions. PCV10 would be more cost-effective than PCV13 with base-case assumptions, but this is sensitive to the price of each vaccine. CONCLUSION: Based on estimated health and economic benefits in children alone, PCV is unlikely to be cost-effective in Croatia. Both vaccines would need to be priced at less than US$ 20 per dose to be considered cost-effective for children. Further analyses should be conducted to estimate the health and economic burden of pneumococcal disease in older age groups, and to assess the influence on cost-effectiveness results when short-term and long-term indirect effects are included for older individuals. While there are important uncertainties around the price and effectiveness of both vaccines, our analysis suggests there is insufficient evidence to warrant a significant difference in the price of the two vaccines