Efekti lasero-terapije na intrakanalni dentin i cementno tkivo apeksa korena zuba

Laser irradiation during root canal treatment is efficient but in order to prevent irreversible thermal damage to dentine, cementum and other periapical structures continuous water cooling is required. The aim of this study was to ultrastructurally analyze the surface of intracanal dentine and cementum at the root apex after Er:YAG laser irradiation with and without sterile saline solution irrigation. The study involved 70 intact maxillary and mandibular single-rooted and tworooted human teeth, divided into two experimental groups and one control group. In all teeth access cavity was created. For root canal irradiation, Er:YAG laser with the wavelength of 2940 nm, energy output of 140 mJ per pulse, pulse duration of 125-160 ms, pulse repetition rate of 10 Hz and power of 15 W was used. Total irradiation time for each root canal was 10 seconds. The ultrastructural analysis of intracanal dentine and the cementum of the root apex was done by using scanning electron microscope (JEOL JSM-5300 Tokyo Japan). Intracanal Er:YAG laser irradiation without water cooling showed melted circumpulpal dentine with large cracks in it, whereas cementum at the root apex was thermally modified in the form of plates and cracks. Intracanal Er:YAG laser irradiation with continuous water cooling resulted in clean intracanal dentine surface without morphological changes of the cementum. The canal system irradiation is acceptable and possible only when using constant water cooling; otherwise, irreversible thermal damage to intracanal dentine and cementum at the root apex occur.Obrada kanala korena zuba laserom je efikasna, ali zahteva obavezno hlađenje vodom kako bi se sprečila ireverzibilna termička oštećenja dentina, cementa i ostalih periapeksnih struktura. Cilj ovog rada bio je da se ultrastrukturno analizira površina intrakanalnog dentina i cementnog tkiva na apeksu korena zuba posle obrade kanala Er:YAG laserom bez irigacije i sa irigacijom sterilnim fiziološkim rastvorom. Korišćeno je 70 intaktnih maksilarnih i mandibularnih jednokorenih i dvokorenih humanih zuba, podeljenih u dve eksperimentalne i jednu kontrolnu grupu. Kod svih zuba je formiran pristupni kavitet. Za obradu kanala korišćen je Er:YAG laser talasne dužine 2940 nm, izlazne energije za impuls 140 mJ; u pulsnom režimu 125-160ms, stopom pulsne repeticije od 10 Hz i energijom od 15 W. Vreme obrade svakog kanala laserom iznosilo je 10 sekundi. Ultrastrukturna analiza intrakanalnog dentina i cementnog tkiva na apeksnom delu korena zuba urađena je na skening elektronskom mikroskopu (JEOL JSM -5300 Tokyo Japan). Intrakanalna obrada Er:YAG laserom bez vodenog hlađenja pokazuje stopljen cirkumpulparni dentin sa velikim pukotinama u dentinu, a cementno tkivo na apeksu je termički modifikovano u vidu ploča i pukotina. Intrakanalna obrada Er:YAG laserom uz kontinuirano vodeno hlađenje daje čistu intrakanalnu dentinsku površinu bez morfoloških promena cementnog tkiva. Obrada kanalnog sistema zuba je opravdana i moguća samo u uslovima stalnog hlađenja vodom, u protivnom nastaju ireverzibilna termička oštećenja intrakanalnog dentina i cementa na apeksu korena zuba

The future (and the present) of motor vehicle propulsion systems

Limited reserves of oil and the increasing environmental effect of its usage as a motor fuel represent global issue related to the constantly increasing number of motor vehicles. Therefore, the reduction of the fossil fuel consumed and the emission produced in internal combustion engines is the primary goal of the development of motor vehicle propulsion systems. In that sense, the present and the future of motor vehicles relies on hybrid drive systems, electric drive systems and drive systems which use hydrogen as a fuel (either by its combustion or by production of electric energy with the help of fuel cells). In this paper, the authors have presented the aforementioned motor vehicle propulsion systems by explaining their function and design, their basic elements and their functions. Authors have also analysed advantages and disadvantages of the mentioned propulsion systems in comparison to conventional internal combustion engine based systems, both technically and environmentally speaking, but also in relation to available infrastructure and energy resources

Advanced theoretical-experimental method for optimization of dynamic behavior of firefighting vehicle modular superstructures

U radu je predstavljena teorijsko-eksperimentalna metoda razvijena sa ciljem optimizacije dinamičkog ponašanja modularnih nadgradnji vatrogasnih vozila. Teški uslovi eksploatacije u kojima se vatrogasna vozila koriste, kao i posebni zahtevi za ovu vrstu vozila zahtevaju posvećenost u pristupu optimizaciji nadgradnji sa stanovišta napona, deformacija, zamora, buke, kao i udobnosti i efektivnosti vozila. Optimizacija podrazumeva izbor optimalnih oblika, materijala, dimenzija, veza, oslanjanja, prigušenja i izolacije modula, sa ciljem postizanja optimalnog dinamičkog ponašanja nadgradnje. Metoda opisana u radu sastoji se od dva međusobno povezana dela - teorijskog i eksperimentalnog. Teorijski deo sastoji se od numeričkog modeliranja varijanti nadgradnje i proračuna odziva na dinamičke pobude korišćenjem metode konačnih elemenata, čiji se rezultati naknadno verifikuju kroz eksperimente. Eksperimentalni deo zasniva se na pobudi fizičkih modela nadgradnji pomoću posebno razvijenog mehaničkog pobudnog uređaja, praćenju odziva nadgradnji, kao i promeni ulaznih parametara u procesu projektovanja nadgradnji, sa ciljem dobijanja nadgradnje sa što boljim dinamičkim karakteristikama. Sopstvene frekvencije nadgradnje, važne u smislu rezonantnih zona, dobijene su korišćenjem testa udarom i FFT analize. Ova metoda se pokazala adekvatnom za optimizaciju dinamičkog ponašanja modularnih nadgradnji, kao što su one kod vatrogasnih vozila. Celokupna ispitna instalacija korišćena kroz ovu metodu ilustrativno je prikazana u radu. Takođe, date su smernice za dalje aktivnosti, razvoj i unapređenje ove metode.This paper shows elaborated theoretical-experimental method used to optimize dynamic behavior of modular superstructures of firefighting vehicles. Harsh exploitation conditions under which firefighting vehicles operates and special requirements for this type of vehicles require dedicated approach to optimization of superstructures in terms of stress, deformation, fatigue, noise, comfort and effectiveness. Optimization implies selection of optimal shapes, materials, dimensions, mountings, suspension, damping and insulation of modules to attain optimal dynamic behavior of superstructure. Method described in this paper can be divided into two interconnected parts - theoretical and experimental. Theoretical part consists of numerical modeling of superstructure variants and calculation of their responses to dynamic excitations using FEM, whose results are later validated through experiments. Experimental part of this method is based on excitation of superstructure physical models with, for this purpose specially developed, mechanical exciter, monitoring of superstructure response and changing of the input parameters in the design of superstructure to create the superstructure with best possible dynamic characteristics. Natural frequencies of structures, important in terms of resonant zones, are obtained using bump tests and FFT analysis. This method has proved suitable for optimization of dynamic behavior of modular superstructures such as those of firefighting vehicles. Complete testing installation used in this method is illustratively shown in this paper. Also, there are guidelines for further development and improvement of this method

Advanced theoretical-experimental method for optimization of dynamic behavior of firefighting vehicle modular superstructures

U radu je predstavljena teorijsko-eksperimentalna metoda razvijena sa ciljem optimizacije dinamičkog ponašanja modularnih nadgradnji vatrogasnih vozila. Teški uslovi eksploatacije u kojima se vatrogasna vozila koriste, kao i posebni zahtevi za ovu vrstu vozila zahtevaju posvećenost u pristupu optimizaciji nadgradnji sa stanovišta napona, deformacija, zamora, buke, kao i udobnosti i efektivnosti vozila. Optimizacija podrazumeva izbor optimalnih oblika, materijala, dimenzija, veza, oslanjanja, prigušenja i izolacije modula, sa ciljem postizanja optimalnog dinamičkog ponašanja nadgradnje. Metoda opisana u radu sastoji se od dva međusobno povezana dela - teorijskog i eksperimentalnog. Teorijski deo sastoji se od numeričkog modeliranja varijanti nadgradnje i proračuna odziva na dinamičke pobude korišćenjem metode konačnih elemenata, čiji se rezultati naknadno verifikuju kroz eksperimente. Eksperimentalni deo zasniva se na pobudi fizičkih modela nadgradnji pomoću posebno razvijenog mehaničkog pobudnog uređaja, praćenju odziva nadgradnji, kao i promeni ulaznih parametara u procesu projektovanja nadgradnji, sa ciljem dobijanja nadgradnje sa što boljim dinamičkim karakteristikama. Sopstvene frekvencije nadgradnje, važne u smislu rezonantnih zona, dobijene su korišćenjem testa udarom i FFT analize. Ova metoda se pokazala adekvatnom za optimizaciju dinamičkog ponašanja modularnih nadgradnji, kao što su one kod vatrogasnih vozila. Celokupna ispitna instalacija korišćena kroz ovu metodu ilustrativno je prikazana u radu. Takođe, date su smernice za dalje aktivnosti, razvoj i unapređenje ove metode.This paper shows elaborated theoretical-experimental method used to optimize dynamic behavior of modular superstructures of firefighting vehicles. Harsh exploitation conditions under which firefighting vehicles operates and special requirements for this type of vehicles require dedicated approach to optimization of superstructures in terms of stress, deformation, fatigue, noise, comfort and effectiveness. Optimization implies selection of optimal shapes, materials, dimensions, mountings, suspension, damping and insulation of modules to attain optimal dynamic behavior of superstructure. Method described in this paper can be divided into two interconnected parts - theoretical and experimental. Theoretical part consists of numerical modeling of superstructure variants and calculation of their responses to dynamic excitations using FEM, whose results are later validated through experiments. Experimental part of this method is based on excitation of superstructure physical models with, for this purpose specially developed, mechanical exciter, monitoring of superstructure response and changing of the input parameters in the design of superstructure to create the superstructure with best possible dynamic characteristics. Natural frequencies of structures, important in terms of resonant zones, are obtained using bump tests and FFT analysis. This method has proved suitable for optimization of dynamic behavior of modular superstructures such as those of firefighting vehicles. Complete testing installation used in this method is illustratively shown in this paper. Also, there are guidelines for further development and improvement of this method

Fractal Corrections of BaTiO3-ceramic Sintering Parameters

Morphology of ceramics grains and pores as well as Brownian character of particle dynamics inside ceramics specimen contributes to better understanding of the sintering process. BaTiO3-ceramics, studied in this paper, has light fractal form and it is emanated in three aspects. First, the surface of grains, even in starting green body as well as distribution of grains shows fractal behavior. Second, existence of pores and their distribution follow the rules of fractal geometry. Third, movement of particles inside viscous flow underlies the rule of Brownian motion, which is essentially a fractal category. These three elements, each in its domain influence sintering dynamics, and can be described by dimensionless quantitative factors, alpha(S), alpha(P) and alpha(M), being normalized to the interval [0,1]. Following sintering process, the associate formulae of Frenkel, Scherer and Mackenzie-Shuttleworth are shown from the angle of view of ceramics fractal dimension changing that approaches to 3. Also, it is shown that the energy balance is not violated after applying fractal correction to quasi equilibrium of the energy emanating from surface area reduction E-S and energy adopted by viscous flow E-f

System Approach to Vehicle Suspension System Control in CAE Environment

In recent years, motor vehicles industry has shown a tendency of replacing electromechanical components by mechatronic systems with intelligent and autonomous properties. The integration of hardware components and implementation of advance control function characterize this replacement. In this paper we have applied the system approach and system engineering methods in the initial phase of vehicle active suspension development. An emphasis has been placed upon the interrelations between computer-aided simulation and other elements of the development process. The benefits of application of active suspension simulation are numerous: reduction of time to market, the new and improved functions of mechatronic components/devices, as well as the increased system reliability. In suspension model development, we used CAD/CAE tools, as well as the multipurpose simulation programs. For simulation, we used the one-quarter vehicle model. The modelling was carried out through the state-space equation, after which we designed the controller for our system. During this, we considered only the digital systems of automatic regulation

The future (and the present) of motor vehicle propulsion systems

Limited reserves of oil and the increasing environmental effect of its usage as a motor fuel represent global issue related to the constantly increasing number of motor vehicles. Therefore, the reduction of the fossil fuel consumed and the emission produced in internal combustion engines is the primary goal of the development of motor vehicle propulsion systems. In that sense, the present and the future of motor vehicles relies on hybrid drive systems, electric drive systems and drive systems which use hydrogen as a fuel (either by its combustion or by production of electric energy with the help of fuel cells). In this paper, the authors have presented the aforementioned motor vehicle propulsion systems by explaining their function and design, their basic elements and their functions. Authors have also analysed advantages and disadvantages of the mentioned propulsion systems in comparison to conventional internal combustion engine based systems, both technically and environmentally speaking, but also in relation to available infrastructure and energy resources

Application of the intergranular impedance model in correlating microstructure and electrical properties of doped BaTiO3

Microstructure properties of barium-titanate based materials, expressed in grain boundary contacts, are of basic importance for electric properties of this material. In this study, the model of intergranular impedance applied on a two-grain contact is considered. Globally, a BaTiO3-ceramics sample consists of a large number of mutually contacted grains, which form clusters. Such clusters can be presented as specific fractal formations. For each of them, it is possible to establish the equivalent electrical model and, for a defined set of input parameters, using symbolic analysis, obtain the frequency diagram. The influence of fractal structure is especially stressed. Realizing the totality of relations between cluster grain groups, their microelectrical schemes and corresponding frequency characteristics, on one hand, and the global equivalent electrical scheme and corresponding acquired frequency characteristics of BaTiO3-ceramics samples, on the other hand, we set a goal of correlating experimental results with the summing effect of microelectric equivalent schemes. The model is successfully tested on doped barium-titanate ceramics.Mikrostrukturna svojstva materijala na bazi barijum-titanata, izražena kontaktima granica zrna od fundamentalne su važnosti za električna svojstva ovih materijala. U ovom radu razmatrana je primena modela impedanse između dva zrna na kontakt dva zrna. Globalno posmatrano, uzorak BaTiO3-keramike sastoji se od ogromnog broja zrna u međusobnom kontaktu koji formiraju klastere. Takvi klasteri mogu biti predstavljeni kao specifične fraktalne formacije. Za svaku od ovih formacija moguće je uspostaviti ekvivalentni električni model za definisani set ulaznih parametara koristeći metod simboličke analize i dobiti odgovarajuću frekventnu karakteristiku. Posebno je naglašen uticaj fraktalne strukture. Realizujući kompletnu relaciju između klastera zrna, njihovih mikroelektričnih šema i odgovarajućih frekventnih karakteristika s jedne strane, i globalnih ekvivalentnih električnih šema i odgovarajućih frekventnih karakteristika uzoraka BaTiO3-keramike, s druge strane, uspostavljamo set ciljanih koincidentnih eksperimentalnih rezultata sa sumarnim efektima izračunavanih mikroelektričnih ekvivalentnih šema. Model je uspešno testiran na uzorcima barijum-titanatne keramike

VERIFICATION OF CALCULATION METHOD FOR DRONE MICRO-DOPPLER SIGNATURE ESTIMATION

Drones micro-Doppler signatures obtained by FMCW radars are an excellent procedure for malicious drone detection, identification and classification. There are a number of contributions dealing with recorded spectrograms with these micro-Doppler signatures, but very low number of them has analyzed possibility to calculate echo caused by drone moving parts. In this paper, starting from already existing mathematical apparatus, we presented such spectrograms as a function of changing drone moving parts characteristics: rotor number, blades number, blade length and rotor moving speed. This development is the part of a wider project intended to prevent malicious drone usage