The influence of mechanical oscillations on safety of funcioningof testile machines

Analiza sigurnosti funkcionisanja sastavnih komponenti sklopa boksa predenja i sklopa za namotavanje kalemova gotovom pređom kod OE - predilice se može najpreciznije pratiti formiranjem monitoring sistema praćenja njihovog rada. Na osnovu nje vrše se procedure preventivnog održavanja, koje se baziraju na konceptu planskog održavanja koje obuhvataju ocene stvarnog stanja rada i ispravnosti sastavnih komponenti analiziranih sklopova. Ovaj vid praćenja stanja obuhvata korelacionu povezanost pouzdanosti i nivoa mehaničkih oscilacija na sastavnim komponentama analiziranih sklopova i uzroke koje one dovode do njihovih otkaza. Korelacija je izvršena formiranjem univerzalnog optimalnog modela rada analiziranih sklopova prema izabranim mernim mestima na osnovu uticaja mehaničkih oscilacija (vibracija). Metodologija praćenja stanja je obuhvatila nivoe amplitudnih spektra mernih veličina oscilovanja na komponentama analiziranih sklopova za izvršena redosledna merenja. Dobijene vrednosti su unešene u univerzalni optimalni model za različite vremenske intervale rada komponenata analiziranih sklopova, pa je na osnovu njih određena zavisnost modela u funkciji eksploatacionog vremena (t) , koja predstavlja određivanje frekventne sigurnosti rada sklopova. Ova zavisnost podržala je ocenu sigurnosti funkcionisanja sastavnih komponenti analiziranih sklopova u slučajevima kada na njima nisu sprovođeni postupci tehnologije preventivnog održavanja i kada su ovi postupci sprovođeni.The analysis of functioning of basic components of technical system is the basic type of monitoring systems and state analyzing. Based on this, there are procedures of preventive maintenance, which have the grades of real state of work and components of technical system. This work contains co-relation between levels of mechanical oscillations of components in the system and their influence on the cause of system mallfunction. Corelation is based on forming the universal optimal working model for analvzing the system on chosen measurement points based on the influence of mechanical oscillations (vibrations). The methodology of state tracking has levels of amplitude spectres of measurement values and oscillating the components of analized systems for those results. The values are the input for basic universal optimal model for different time intervals of system work, and based on those values were defmite the model dependence in the time oscillations (t), which represents the dependence of frequent safety of sub - system in function of their work)).These dependence is supported in the functioning of basic components of analized system in the čaše of their work with and without the basic maintenance

Possible Therapeutic Use of Spermatogonial Stem Cells in the Treatment of Male Infertility: A Brief Overview

Development of germ cells is a process starting in fetus and completed only in puberty. Spermatogonial stem cells maintain spermatogenesis throughout the reproductive life of mammals. They are undifferentiated cells defined by their ability to both self-renew and differentiate into mature spermatozoa. This self-renewal and differentiation in turn is tightly regulated by a combination of intrinsic gene expression as well as the extrinsic gene signals from the local tissue microenvironment. The human testis is prone to damage, either for therapeutic reasons or because of toxic agents from the environment. For preservation of fertility, patients who will undergo radiotherapy and/or chemotherapy have an attractive possibility to keep in store and afterwards make a transfer of spermatogonial stem cells. Germ cell transplantation is not yet ready for the human fertility clinic, but it may be reasonable for young cancer patients, with no other options to preserve their fertility. Whereas this technique has become an important research tool in rodents, a clinical application must still be regarded as experimental, and many aspects of the procedure need to be optimized prior to a clinical application in men. In future, a range of options for the preservation of male fertility will get a new significance

Uloga policije u ostvarivanju bezbednosti na međunarodnim plovnim rekama u Srbiji

The police role in achieving security in the international river waterways is observed only with respect to security issues which are dealt with by the police officers in the police stations and police branch offices of the district police departments through the territory of which the international river waterways flow, as well as the police officers and police branch offices in charge of river security in Belgrade. The Ministry of the Interior of the Republic of Serbia, generally speaking, has a much larger role as a security component. This means taking into account that certain areas of security jobs and tasks related to the international river waterways are also performed by other organizational units of the Ministry: Sector for Emergency Management, Special Anti-Terrorist Unit, Anti-Terrorist Unit, Diving Center of Gendarmerie, Department of Border Police and other, but in those cases the cooperation with the Police Department for the city of Belgrade, police branch offices of the district police departments and the general jurisdiction police should not be neglected. The international river waterways in Serbia are around 1000 kilometers long (the river Danube is navigable 588 km in length, the Sava 207 km, and the Tisa 168 km) and are only a part of internal navigation waterways in Serbia. In addition, the improvement and increase of security level in these waters in Serbia is an area that will be more intensively reviewed, analyzed and developed in the following period.Uloga policije u ostvarivanju bezbednosti na međunarodnim plovnim rekama obrađena je samo u pogledu bezbednosne problematike kojom se bave policijski službenici u policijskim stanicama i policijskim ispostavama područnih policijskih uprava kroz čiju teritoriju protiču međunarodne plovne reke i odvija se međunarodna i unutrašnja plovidba, kao i policijski službenici PI za bezbednost na rekama u Beogradu. Šire gledano, uloga MUP-a Republike Srbije kao subjekta bezbednosti znatno je veća, imajući u vidu da određene segmente poslova i zadataka bezbednosti na međunarodnim plovnim rekama obavljaju i druge organizacione jedince Ministarstva i to: Sektor za vanredne situacije, SAJ, PTJ, Ronilački centar žandarmerije, Uprava granične policije i dr., ali i u tim slučajevima ne treba zanemariti saradnju sa Policijskom upravom za grad Beograd, područnim policijskim upravama i policijom opšte nadležnosti. Međunarodne plovne reke u Srbiji protežu se u dužini od oko 1.000 km (reka Dunav u dužini od 588 km, Sava 207 km i Tisa 168 km) i samo su deo unutrašnjih voda i vodnih puteva u Srbiji. Takođe, unapređenje i povećanje nivoa bezbednosti na unutrašnjim vodama u Srbiji oblast je koja se će se u narednom periodu još intenzivnije razmatrati, analizirati i razvijati

Uloga policije u ostvarivanju bezbednosti na međunarodnim plovnim rekama u Srbiji

The police role in achieving security in the international river waterways is observed only with respect to security issues which are dealt with by the police officers in the police stations and police branch offices of the district police departments through the territory of which the international river waterways flow, as well as the police officers and police branch offices in charge of river security in Belgrade. The Ministry of the Interior of the Republic of Serbia, generally speaking, has a much larger role as a security component. This means taking into account that certain areas of security jobs and tasks related to the international river waterways are also performed by other organizational units of the Ministry: Sector for Emergency Management, Special Anti-Terrorist Unit, Anti-Terrorist Unit, Diving Center of Gendarmerie, Department of Border Police and other, but in those cases the cooperation with the Police Department for the city of Belgrade, police branch offices of the district police departments and the general jurisdiction police should not be neglected. The international river waterways in Serbia are around 1000 kilometers long (the river Danube is navigable 588 km in length, the Sava 207 km, and the Tisa 168 km) and are only a part of internal navigation waterways in Serbia. In addition, the improvement and increase of security level in these waters in Serbia is an area that will be more intensively reviewed, analyzed and developed in the following period.Uloga policije u ostvarivanju bezbednosti na međunarodnim plovnim rekama obrađena je samo u pogledu bezbednosne problematike kojom se bave policijski službenici u policijskim stanicama i policijskim ispostavama područnih policijskih uprava kroz čiju teritoriju protiču međunarodne plovne reke i odvija se međunarodna i unutrašnja plovidba, kao i policijski službenici PI za bezbednost na rekama u Beogradu. Šire gledano, uloga MUP-a Republike Srbije kao subjekta bezbednosti znatno je veća, imajući u vidu da određene segmente poslova i zadataka bezbednosti na međunarodnim plovnim rekama obavljaju i druge organizacione jedince Ministarstva i to: Sektor za vanredne situacije, SAJ, PTJ, Ronilački centar žandarmerije, Uprava granične policije i dr., ali i u tim slučajevima ne treba zanemariti saradnju sa Policijskom upravom za grad Beograd, područnim policijskim upravama i policijom opšte nadležnosti. Međunarodne plovne reke u Srbiji protežu se u dužini od oko 1.000 km (reka Dunav u dužini od 588 km, Sava 207 km i Tisa 168 km) i samo su deo unutrašnjih voda i vodnih puteva u Srbiji. Takođe, unapređenje i povećanje nivoa bezbednosti na unutrašnjim vodama u Srbiji oblast je koja se će se u narednom periodu još intenzivnije razmatrati, analizirati i razvijati

Ultrasound assessment of the effect of fetal position on supine to prone righting reflex in the guinea pig fetus

The aim of the study was to assess the effect of guinea pig fetal position on the righting reflex from a supine to prone position using ultrasound examination. Experimental and control group were formed, each encompassing 20 pregnant females with 50 fetuses from the 31st to 66th day of gestation. During ultrasound examination, the fetuses from the experimental group were brought into a supine position relative to gravity by placing the dams in the appropriate position. In the control group fetuses were examined for changes in position irrespective of gravity as well as for changes in position after having been brought into a prone position relative to gravity. Comparison of the experimental and the control group showed that experimental group fetuses in the oldest bracket rotated successfully to a prone position more frequently than at other ages. The observed fetal movements indicate that the fetus changes its position using the contact-righting reflex

Improving the Operational Reliability Model of the “Nikola Tesla-Block A” Thermal Power Plant System by Applying an Integrated Maintenance Model

The evaluation of the reliability status of complex technical systems is of great importance for their uninterrupted operation at full capacity and with a preventive maintenance plan in place. Limited research on the subject indicates that there is need to improve models of reliability simulation. The goal of the paper is to outline an improved operational reliability model of a thermal power plant using the power plant block “TENT A” as an example. The model is based on the failure interaction of the system components and is based on probability theory - the Weibull distribution, the Monte Carlo simulation and the established mathematical models of failure interaction of components using new software solutions. The results of the simulations show which direction the development of preventive activities should take in the case of failure interaction, which might lead to minimum downtime in power plant operations in the future

The Impact of Soil Microplastic on Insect Diversity and Plastic Decomposition by Insects

Plastic has been recognized as one of the leading pollutants of all ecosystems. This question has been rarely raised in Serbia, although there is a significant problem with the disposal of communal and agricultural waste. Many wild landfills have been created in past decades in forests near the plasticulture practicing areas and rivers. Plastic materials are degraded by the influence of UV light and various environmental factors, creating smaller particles called microplastics, which are recognized as significantly dangerous to ecosystems. Alluvial planes have been the most endangered due to the horizontal and vertical fluvial activities of the nearby rivers. The influence of soil microplastics on insect communities has not been widely considered and that is why the project EMIPLAST-SoS has been created to investigate insect communities in polluted and unpolluted alluvial soils in Serbia. We compare them in forest and agricultural ecosystems on similar alluvial soils in three locations near three largest rivers in Serbia. Preliminary results from one-season sampling are considered. During the project the influence of the different seasons effects will be investigated. Additionally, we have investigated the rate of plastic decomposition by five insect species in lab conditions (Plodia interpunctella Hubner, Tenebrio molitor L., Zophobas morio Fabr., Achroia grisella Fabr. and Galleria mellonela L.). G. mellonela expressed the highest and the most diverse decomposition of different plastic sources like plastic bags, sponges and styrofoam. The analyses of the obtained plastic residues are still underway

Стари Грци : портрет једног народа : [представљање књиге на Трибини Библиотеке САНУ, Београд, 8. новембра 2011. године]

Стари Грци : портрет једног народа / Иван Јордовић. – Београд : Балканолошки институт САНУ : Завод за уџбенике, 2011. Говорили: академик Никола Тасић, проф. др Слободан Г. Марковић, проф. др Данијела Стефановић и проф. др Иван Јордовић. У Београду, уторак 8. новембар 2011. у 13.00 часов

Fuzzy logic expert system for calculating the parameters of coupled numerical analysis of the fluid and thin-walled structures interaction

U radu su prikazani rezultati numeričkih proračuna interakcije fluid-struktura korišćenjem diskretizacionih numeričkih metoda - metode konačnih elemenata za proračun naponsko-deformacionog stanja zida kanala i metode konačnih zapremina za numerički proračun dinamike fluida. Na osnovu dobijenih rezultata razvijen je fazi ekspertski sistem za procenu izlaznih parametara numeričkog proračuna, prikazane su osnovne karakteristike razvijenog fazi modela i rezultati dobijeni njegovom primenom. Analizirani su uticaji tri ulazna parametra - temperature unutrašnje površine zida kanala, razlike između temperatura unutrašnje i spoljašnje površine zida i faktora koji definiše gustinu numeričkih mreža - na dva izlazna parametra: vrednost pada statičkog pritiska niz struju i vrednost maksimalnih kombinovanih Fon Misesovih napona ostvarenih u strukturi kanala za zadate uslove opterećenja. Na osnovu dobijenih rezultata vidimo da formirani fazi ekspertski sistem može sa zadovoljavajućom tačnošću biti iskorišćen za procenu posmatranih izlaznih veličina, pri znatno kraćem vremenu potrebnom za proračun i uz angažovanje resursa računarskog sistema u značajno manjem obimu.This paper deal with structural deformation of one rectangular, closed, thin walled, steel made, thermally loaded channel and influence of this deformation on the air flow through the channel, recognised as coupled fluid-structure interaction problem. The geometrically non-linear deformation of thermally loaded channel was solved using commercial finite-element analysis software ANSYS. The unsteady Navier-Stokes equations in their conservation form defining fluid flow are solved using commercial computer fluid dynamics software ANSYS CFX. A fuzzy logic-based expert system has been developed to predict some results of structural and fluid flow numerical simulation instead of directly evaluating it by a time-consuming software coupling of finite-element and computer fluid dynamics numerical analysis. Three input parameters, namely temperature of channel inner walls, difference in temperature of inner and outer surface of channel wall, and factor of mesh size, are varied while solving the fluid-structure interaction problem. A pressure drop downstream the flow was considered as a computer fluid dynamics output parameter of importance, while Von Misses maximum stresses were an finite-element analysis output parameter observed. The developed FLES can predict the results of finite-element and computer fluid dynamics analysis, a pressure drop and Von Misses maximum stresses respectively, within a reasonable accuracy limit and at lower computation cost compared to the finite-element, and CFD computer fluid dynamics packages combined into series of multi-physics analyses

Impact of plastic pollution on soil biological activity in white truffle habitats in the large river plains in Serbia

The impact of plastic pollution on forest soil biota is an emerging research area. There are knowledge gaps on a forest microbiome composition and activity as effected by wild waste deposition in forest ecosystems located on white truffle (Tuber magnatum Pico) habitat areas. Particles of plastic materials decompose into micro-plastic particles and are responsible for many changes in the soil physicochemical characteristics, including porosity, enzymatic activities, microbial activities, plant growth. One of the first investigations of plastic and microplastic (MP) in the soil on the territory of Serbia is currently underway and is being carried out within the project "Evaluation of the Microplastic in the Soils of Serbia - EMIPLAST - SoS". The research sites are located on the alluvial plains of the largest rivers in Serbia, which are the habitats of the white truffle. Forest sites visibly polluted and non-polluted by plastic materials were sampled and analysed for soil main chemical, physical and biological properties. Potentially mineralizable soil organic carbon was measured in a long-term incubation of soil samples with sequential measurement of the emitted CO2 flax by alkali trap method. Preliminary results showed that some soil properties such as pH, electrical conductivity, total C and N, CEC and mechanical composition are significantly affected by the presence of plastic materials. Generally, polluted sites showed elevated microbial respiration and the rates of C mineralization. For the Danube and Morava River basin the differences were significant, while for the Sava river basin the difference wasn’t significant. In order to establish the level of the negative impact of microplastics on soil properties and microbial activity in the longer term, the study is ongoing