Razvoj i implementacija kompjuterskih metoda pri analizi deformacije tijela nosača metodom konačnih elemenata (MKE)

This is a very substantial activity in which designer finds out possible deformations, rigidities (stifnesses) and stress states of the machine parts and fits after forming its virtual geometry, and later the real one as well. They are of the essential importance at the fast and accurate analysis of the possible elastic and plastic body deformation. In this case the point is the solid object of the device beam of an – agro – machine of relatvivelly more complex configuration.Ovo je vrlo bitna aktivnost u kojoj konstruktor utvrđuje moguće deformacije, krutosti i stanja naprezanja strojnih dijelova i sklopova poslje obrazovanja njegove virtuelne, a kasnije i stvarne geometrije. One su od esencijalne važnosti kod brze i točne analize moguće elastične i platične deformacije tijela. U ovom slučaju radi se o solid objektu nosača uređaja agro-stroja, relativno složenije konfiguracije

Razvoj i implementacija kompjuterskih metoda pri analizi deformacije tijela nosača metodom konačnih elemenata (MKE)

This is a very substantial activity in which designer finds out possible deformations, rigidities (stifnesses) and stress states of the machine parts and fits after forming its virtual geometry, and later the real one as well. They are of the essential importance at the fast and accurate analysis of the possible elastic and plastic body deformation. In this case the point is the solid object of the device beam of an – agro – machine of relatvivelly more complex configuration.Ovo je vrlo bitna aktivnost u kojoj konstruktor utvrđuje moguće deformacije, krutosti i stanja naprezanja strojnih dijelova i sklopova poslje obrazovanja njegove virtuelne, a kasnije i stvarne geometrije. One su od esencijalne važnosti kod brze i točne analize moguće elastične i platične deformacije tijela. U ovom slučaju radi se o solid objektu nosača uređaja agro-stroja, relativno složenije konfiguracije

Edem mozga kod zavisnika od droge

Background/Aim. The effect of drugs leaves permanent consequences on the brain, organic in type, followed by numerous manifestations, and it significantly affects the development of mental dysfunctions. The clinicians are often given a task to estimate a patient's personality during treatment or during experts estimate of a drug addict. The aim of this research was to determine the differences, if any, in characteristics of addicts experience and personality traits in drug addicts with or without cerebral edema. Methods. The research was conducted on a sample of 252 male drug addicts, the average age of 23.3 (SD = 4.3) years. Cerebral edema was confirmed on magnetic resonance (MR) images of the brain performed during the treatment of the addicts. The participants were tested by the psychologists using Minnesota Multiphasic Personality Inventory (MMPI-201) test, and the data were processed using canonical discriminate analysis within the SPSS program. The dependent variable in the study was cerebral edema. A block of independent variables, designed for the requirements of this study, consisted of two subgroups. The first one consisted of 12 variables describing the relevant characteristics of drug abuse. The second subgroup consisted of 8 psychopathological tendencies in the personality defined by the mentioned test. Results. Cerebral edema was confirmed in 52 (20.63%) of the drug addicts. The differences between the groups of drug addicts with and without cerebral edema were determined in the following: the time span of taking drugs (0.301), use of alcohol parallel with drugs (0.466), and treatment for addiction (0.603). In the drug addicts with a cerebral edema, MMPI-201 confirmed the increase in the scales for hypochondria, psychopathic deviations and psychastenia, and the decrease in the scales for schizophrenia and depression. Conclusion. Our study confirmed a possible connection between cerebral edema and personality traits in a number of the examined drug addicts. Considering the fact that practice often requires personality estimation, regardless whether it is about treatment or expert's estimate, it is necessary to further research in this direction.Uvod/Cilj. Dejstvo droge ostavlja trajne posledice organskog tipa, na mozak, praćene brojnim neurološkim manifestacijama, i bitno utiče na razvoj psihičkih poremećaja. Kliničarima se često postavlja zadatak da procene ličnost tokom lečenja ili veštačenja zavisnika od droge. Cilj istraživanja bio je utvrđivanje karakteristika narkomanskog staža i osobina ličnosti kod zavisnika od droge sa i bez edema mozga. Metode. Istraživanje je sprovedeno u grupi od 252 zavisnika od droge muškog pola, prosečne starosti 23,3 (SD = 4,3) godine. Za vreme lečenja zavisnika od droge rađena je magnetna rezonanca mozga, a za procenu psihopatoloških tendencija ličnosti korišćen je Minnesota Multiphasic Personality Inventory (MMPI-201) test. Za obradu podataka korišćena je kanonička diskriminativna analiza u sklopu SPSS programa. Zavisna varijabla u istraživanju bio je edem mozga. Blok nezavisnih varijabli, sačinjen za potrebe ovog istraživanja, sastojao se od dve podgrupe. Prvu je činilo 12 varijabli kojima se opisuju relevantna obeležja zavisnosti od droga. Drugu je činilo 8 psihopatoloških tendencija ličnosti definisanih pomenutim testom. Rezultati. Edem mozga utvrđen je kod 52 (20,63%) zavisnika od droge. Razlike između grupa zavisnika od droge sa i bez edema mozga utvrđene su u dužini narkomanskog staža (0,301), korišćenju alkohola paralelno sa drogama (0,466) i lečenju zavisnosti (0,603). Kod zavisnika od droge sa cerebralnim edemom na MMPI-201 testu utvrđene su povišene skale hipohondrije, psihopatske devijacije i psihastenije, a sniženje skala šizofrenije i depresije. Zaključak. Kod jednog broja ispitivanih zavisnika od droge potvrđena je sumnja u mogućnost povezanosti edema mozga i osobina ličnosti. S obzirom na to da praksa često iziskuje potrebu za procenom ličnosti, bilo da se radi o lečenju ili veštačenju, neophodno je nastaviti istraživanja u ovom pravcu

Global minimum time for the motion of mechanical systems with limited controls and constraint reactions

Предмет истраживања ове докторске дисертације је формирање нових аналитичконумеричких поступака у циљу одређивања глобалног минимума времена кретања како материјалне тачке, тако и холономних и нехолономних механичких система константне и променљиве масе, са ограниченим управљањима и ограниченим реакцијама веза у општем случају. Посебна пажња у дисертацији биће посвећена одређивању диференцијалних једначина кретања нехолономних механичких система у конфигурационом простору Vm , а затим, водећи рачуна о чињеници да се само оно време које је присутно у једначинама реономних веза и на оним местима где се јавља као последица замене зависних координата помоћу тих веза, може разматрати као допунска координата, изведене су диференцијалне једначине кретања нехолономних механичких система у проширеном конфигурационом простору Vm1 . Формулисани проблеми оптимизације решени су у оквиру теорије оптималног управљања, користећи Понтрјагинов принцип максимума и теорију сингуларних оптималних управљања. У поступку одређивања решења постављеног двотачкастог граничног проблема (TPBVP), неопходно је претходно одредити процену интервала вредности непознатих граничних фазних и спрегнутих координата. Имајући у виду да не постоји теорема о јединствености и егзистенцији решења постављеног TPBVP, природно се намећу следећа питања која ће бити разматрана у оквиру ове докторске дисертације: да ли постоји решење постављеног TPBVP, да ли је могуће, у општем случају, одредити процену интервала вредности свих непознатих граничних фазних и спрегнутих координата, као и да ли се може одредити општи нумерички поступак за одређивање свих могући решења TPBVP? Затим, биће разматрани различити, већ постојећи, нумерички алгоритми (shooting method, Nelder Mead method, genetic algorithm, differential еvolution, simulated annealing, random search, C-GRASP algorithm) у циљу изналажења оптималних вредности параметара који утичу на тачност и брзину конвергенције решења уз дату упоредну анализу решења нумеричких алгоритама за глобалну оптимизацију. Такође, урађене су и одређене модификације постојећих, односно развој нових, у циљу добијања што поузданијег нумеричког алгоритма за глобалну оптимизацију имајући у виду предности и мане већ постојећих нумеричких алгоритама. У досадашњој литератури и публикованим научним радовима нису разматрана постављена питања коју су од суштинског значаја при одређивању глобалног минимума времена кретања како материјалне тачке, тако и холономних и нехолономних механичких система. Одговори на постављена питања, дати у овој докторској дисертацији, представљају крајњи циљ истраживања, а самим тим и научне доприносе успешном реализацијом истих.The research topic of this doctoral thesis is the establishment of new analytical-numerical procedures to determine the global minimum time for the motion of both the particle and the variable and invariable-mass holonomic and nonholonomic mechanical systems, with limited controls and limited reactions of constraints in a general case. Special attention is directed to determining differential equations of motion of nonholonomic mechanical systems in the configuration space Vm and, thereafter, taking into account the fact that only the time which is present in the rheonomic constraints and at the locations where it occurs as a consequence of the substitution of dependent coordinates by the help of these constraints, can be considered as a supplementary coordinate, differential equations of motion of nonholonomic mechanical systems in the extended configuration space Vm1 are derived. The formulated optimization problems are solved within the framework of the optimal control theory, using Pontryagin’s maximum principle and the singular optimal control theory. In the procedure of seeking a solution to a set up two-point boundary value problem (TPBVP), it is needed first to estimate the interval of values of unknown boundary phase and conjugate coordinates. Taking into account that there is not a theorem on the uniqueness and existence of the solution to a set up TPBVP, it is reasonable that some questions are imposed to be considered in this doctoral thesis: Is there a solution to TPBVP, is it possible, in a general case, to estimate the interval of values of all unknown boundary phase and conjugate coordinates, and is it possible to determine a general numerical procedure for determining all potential solutions of TPBVP? Thereafter, considerations involve different, already existing, numerical algorithms (shooting method, Nelder Mead method, genetic algorithm, differential evolution, simulated annealing, random search, CGRASP algorithm) in order to find optimum values of parameters that affect the accuracy and rate of the convergence of solution, along with given comparative analysis of the solutions to numerical algorithms for global optimization. Also, certain modifications are carried out of the existing, i.e. development of new ones, in order to obtain as reliable numerical algorithm as possible for global optimization, keeping in mind advantages and disadvantages of the existing numerical algorithms. In the current literature and published scientific papers the questions posed have not been considered and they are of fundamental importance when determining the global minimum time for the motion of both particle and holonomic and nonholonomic mechanical systems. The responses to posed questions, given in this doctoral thesis, represent the ultimate objective of the research, and thereby a scientific contribution to its successful accomplishment

Planning of designing and installation of mechanical elements at the gear speed reducer on the basis of the parameter technology

The development and implementation of the computer methods at project managing in the part of the planning of designing and installation of mechanical elements with the fit (assembly block) of the gear speed reducer is significant and at present irreplaceable engineering task if it has been realized by the modern parameter technology. There are multifunction uses of this organized group of activities, beginning from the quick changeability of elements still in the phase of designing and constructing, thanks to the characteristics of their associativity, still to the wide basis of standard elements that are incorporated in the very program package. Meanwhile, these activities are not simple, so their realization has to be planned from the stand - point of time, resource and cost of realization. For the very designing and constructing was used AutoCAD Mechanical, and for the design managing Microsoft Project

Efikasni algoritmi kompjuterskih metoda pri utvrđivanju stanja naprezanja kočionih mehanizama metodom konačnih elemenata (MKE)

Designing of the high-performance algorithms by the computer methods at the establishing of the states of stress of the brake mechanisms by the methods of the final elements is very substantial with fast and precise analysis of the state of stress and rigidity of the machine parts and the fits of machine parts affter forming its virtual, and later as well as real geometry. There are multiple reasons for it, and they include: economy, interchangeability and primarily its operating certainty, whose function is unavoidable especially with the parts as the brake mechanisms. To that effect are the results in the designing obtained by final elements analysis (FEA) or similar methods, very useful.Algoritmi su vrlo bitni kod brze i točne analize naprezanja i krutosti strojnih djelova i sklopova poslije obrazovanja njegove virtuelne, a kasnije i stvarne geometrije. Višestruki su razlozi za to, kao što su: ekonomičnost, izmjenljivost djelova a prvenstveno njegova eksploataciona pouzdanost čija je funkcija nezaobilazna naročito kod djelova kao što su kočioni mehanizmi

The designing of the four – component composition of the blend of the polymer fibres on the basis of the numerical simulation

In the paper is presented a part of the project for determining basically permissible the four – component coposition of the (4K) mixture of the polymer fibres on the basis of the numerical simulation. The mathematical models of the composition are developed on the basis of the linear equations. The computer solution of some variants of these models is performed by Gaus procedures in combination with the numerical method of Monte Carlo simulation

The application of autochthonous potential of probiotic lactobacillus plantarum 564 in fish oil fortified yoghurt production

The objective of this work was to investigate the survival of autochthonous, potentially probiotic bacteria Lactobacillus plantarum 564, and the influence of long-chain polyunsaturated fatty acid omega-3 (omega-3 PUFA) fish oil fortification on the sensory quality of yoghurt. Three variants of yoghurt were produced using starter cultures of Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus (Chr. Hansen, Denmark), and the potentially probiotic Lactobacillus plantarum 564 (Culture Collection of the Department for Industrial Microbiology, Faculty of Agriculture, University of Belgrade) as follows: (1) without omega-3 PUPA; (2) with 100 mg/l omega-3 PUFA; and (3) with 200mg/l omega-3 PUFA. The survival of potential probiotic Lb. plantarum 564, the changes of starter bacteria counts, changes of pH values, as well as sensory evaluation, were examined during 3 weeks of yoghurt storage. Cells of Lb. plantarum 564 were maintained at > 10(8) cfug(-1). Starter bacteria counts were > 10(7)cfug(-1) for streptococci and > 10(6) cfug(-1) for lactobacilli. The changes of pH were within normal pH of fermented milks. Sensory evaluation showed that all variants of yoghurt produced with Lb. plantarum 564 and 2 concentrations of omega-3 polyunsaturated fatty acids had a high sensory quality (above 90% of maximal quality), and which did not change significantly throughout the examined storage period. Although the sensory quality of the control sample was evaluated as better, the experimental samples fortified with fish oil were also characterized with very acceptable sensory properties. Results of high viability of potential probiotic Lb. plantarum 564, as well as very acceptable yoghurt sensory properties, indicate that this strain can be successfully used in the production of yoghurt fortified with PUFA omega-3 fish oil as a new functional dairy product