Nikola Hajdin: the most important scientific and professional accomplishments in foreign literature commentaries : on the occasion of his eighty-fifth birthday

During his long scientific and professional activity spanning over half a century and going through different phases, professor Nikola Hajdin obtained results of greater or lesser significance depending on the state of development of science and technology. This overview singles out the results which, in our opinion and that of scientific criticism, rendered a specific contribution to the progress of science and its applications. It is primarily his written work and his structures, predominantly bridges, which signified greater or lesser headway in these areas. Here we have singled out, first and foremost, works which have been acknowledged and highly acclaimed in the country and abroad and which constitute a scientific or constructive contribution to progress. Professor Hajdin’s choices during studies seemed to indicate that he would devote his whole life to scientific work in the field of applied mechanics, especially structural mechanics. However, he soon realized that any significant and valuable effort in structural mechanics, in addition to a theoretical basis, required extensive knowledge of real structures, their development and tendencies substantially influencing scientific endeavor in this area. He realized at a very early stage that these were simultaneous and interactive processes. Many outstanding structural achievements came into being under the influence and with knowledge of applied mechanics, such as the discoveries of French scientists such as Claude-Louis Navier, Barré de Saint-Venant and others, which extensively transformed practical know-how in the field of structures.\ud A feedback effect is visible everywhere. One of the most important is definitely the method of finite elements which sprang from practical needs and theoretical investigation of structures. There are very many examples of both. Such a perception as well as the need for scientists to tackle practical problems and application in design prompted professor Hajdin to take up designing as a parallel activity, one he initially considered to be more of a hobby, and later a serious and responsible job in which he incorporated upon, as this survey will show, the results of his scientific work, with some of the applications serving to verify scientific results. This will be discussed at length, for it is precisely this combination that is the chief characteristic of his work. If one reads only his articles, monographs and books dealing with theory, one will not always be able to see where specific results applied to structures lead. The creative opus of professor Hajdin can be broadly divided into six periods, i.e. six areas in which he gave a contribution to science and its applications, and one can say, indeed a contribution to general progress

Najznačajniji naučni i stručni radovi Nikole Hajdina : u komentarima inostrane literature : u čast osamdeset pet godina života

Najznačajniji naučni i stručni radovi Nikole Hajdina : u komentarima inostrane literature : u čast osamdeset pet godina života / Dragoslav Šumarac, Bratislav Stipanić, Nenad Marković. - Beograd : Institut tehničkih nauka SANU, 2008 (Beograd : Publikum). - 79 str. : ilustr. ; 24 cm\ud \ud ISBN 978-86-80321-17-

Influence of electron motion in target atom on stopping power for low-energetic Ions

In this paper the stopping power was calculated, representing the electrons of the target atom as an assembly of quantum oscillators. It was considered that the electrons in the atoms have some velocity before interaction with the projectile, which is the main contribution of this paper. The influence of electron velocity on stopping power for different projectiles and targets was investigated. It was found that the velocity of the electron stopping power has the greatest influence at low energies of the projectile

Repair and Strengthening of Timber Floors of Pančevo Diocese by Timber–Concrete Coupling Technique

The building of Diocese is located in the very center of Pančevo, at the very corner of the City Park. The object is of a great historic and cultural importance and it has been already in use for two centuries. The object was built in the masonry system, using stones and bricks for the walls, and timber for the floor and roof structure. This paper gives the description of repair and reconstruction of timber floors of 6,5m, by coupling timber and concrete technique. The detailed design concept is shown, based on the theory of coupling elasticity and the concepts of ultimate and serviceability limit state of timber structures (Eurocode 5). For the accepted design model, its numerical verification was carried out by the proper simulation in software ABAQUS 6.11. For timber, concrete and adopted fasteners for their coupling, certain laws of material behaving were adopted, as well as their evaluated and proved mechanical characteristics. All this was done to carry out design procedure. The obtained comparative results were presented, from the aspect of nonlinear stress strain analysis in characteristic sections and zones of applied design model. Finally, a short review of reconstruction based on the previous theoretical-analytical observations was given

NUMERICAL MODELING OF ULTRASONIC WAVE PROPAGATION – BY USING OF EXPLICIT FEM IN ABAQUS

Monitoring of structures implies integration of sensors and actuators, smart materials, data transfer as well as computer analyses and simulations with the purpose of damage detection, localization, assessment and prediction of the state of damage at the certain moment and in time. This paper presents the application of the explicit finite element method for modeling of the wave propagation. The examples of concrete plates and thin steel plates in which the propagation of the Lamb waves occur were analyzed. Explicit finite element method was shown to be very efficient even for the waves in ultrasound range. Efficiency, ease of the use and reliability of the wave propagation modeling by the explicit finite element method can contribute to the development of a new and the improvement of the existing methods for the monitoring of structures.The main purpose of this paper is to demonstrate a waveform propagation model using an explicit FEM in ABAQUS software

Effects of point loads on membrane structures

U radu je prikazano istraživanje utjecaja točkastog opterećenja na membranske konstrukcije. Istraživanje je provedeno na numeričkom modelu tipične membranske konstrukcije. Modelom su obuhvaćena razna točkasta opterećenja, a analizirano je nekoliko parametara konstrukcije kako bi se odredilo ponašanje membrane pri djelovanju točkastog opterećenja. Dobiveni rezultati pokazuju da točkasto opterećenje utječe na membranske konstrukcije znatno drugačije nego što je to slučaj kod površinskog opterećenja. Glavni utjecaji točkastog opterećenja na membransku konstrukciju su promjena geometrije konstrukcije te promjena membranskih sila.A research focusing on the effects of point load on membrane structures is presented in the paper. The research was conducted on a numerical model of a typical membrane structure. Different point loads were applied to the model, and several structural parameters were monitored so as to define membrane behaviour under point load. The results show that point loads influence membrane structures in a significantly different way compared to area loads. The main repercussions of point loads on the membrane structure are the change in geometry of the structure and the change of membrane forces

Main criteria for models of excellence in health care

Business excellence models have a long history of development of sixty years. Today, the business excellence model can be essentially classified as world’s most famous models/awards for excellence (Japanese, American and European), the most popular national models of excellence (the Australian, British, German, French), as well as models of excellence companies (Siemens, Philips, Toyota). In the world today there are about 120 models of excellence. The best way to improve quality of health organizations that have systems of quality management is by application of the concept of total quality (TQM). This approach ensures the improvement of overall performance of health organizations, primarily the internal organization including management, resources, processes and human resources, health services and performance of business results. The market requires high quality products and services to improve the quality of life, or TQM excellence models in all areas of social subjects operations. It is a process that never ends, and knowing the nature of man who was never satisfied with achieved, that is main driving force for social development. We are witnesses today that some countries are introducing awards to organizations which succeeded in implementation of TQM and models of excellence for quality achievement. The development of a model of business excellence (BE) for dental health care is the main subject of the current study. The aim of this study is to present and analyze the existing criteria for product excellence and based on that, to define criteria for models of excellence for dental health care in Serbia

Diffraction pattern of the light on track in track detectors

U ovom radu razvijen je model i programski kod za formiranje difrackione slike svetlosti, koja prolazi kroz tragove u čvrstim trag detektorima. Prostiranje svetlostnog talasa, koji prolazi kroz trag, modelovan je na osnovu Hajgens-Frenolovog principa. Napisan je programski kod da se ispita promena difrackione slike svetlosti u zavisnosti od promene parametara traga. Cilj rada je da se na osnovu difrackione slike traga odrede parametri traga čestice u trag detektorima.The model and program code for creation of diffraction pattern of the light, when passes through track in solid state track detectors were developed in the paper. Wave-light was modelled according to Huygens-Fresnel principle. The program code was developed for correlation of diffraction pattern and track parameters. The developed model can be applied for analysis of tracks in track detectors.Зборник радова : XXIX симпозијум ДЗЗСЦГ : Сребрно језеро, 27-29. септембар 2017. годин

Diffraction pattern of the light on track in track detectors

U ovom radu razvijen je model i programski kod za formiranje difrackione slike svetlosti, koja prolazi kroz tragove u čvrstim trag detektorima. Prostiranje svetlostnog talasa, koji prolazi kroz trag, modelovan je na osnovu Hajgens-Frenolovog principa. Napisan je programski kod da se ispita promena difrackione slike svetlosti u zavisnosti od promene parametara traga. Cilj rada je da se na osnovu difrackione slike traga odrede parametri traga čestice u trag detektorima.The model and program code for creation of diffraction pattern of the light, when passes through track in solid state track detectors were developed in the paper. Wave-light was modelled according to Huygens-Fresnel principle. The program code was developed for correlation of diffraction pattern and track parameters. The developed model can be applied for analysis of tracks in track detectors.Зборник радова : XXIX симпозијум ДЗЗСЦГ : Сребрно језеро, 27-29. септембар 2017. годин

Analiza distribucije opterećenja kod mešovito nošenih mostova primenom rezilijentnih abatmenata

Introduction Differences between the tooth and implant response to load can lead to many biological and technical implications in the conditions of occlusal forces. Objective The objective of this study was to analyze load distribution in tooth/implant-supported fixed partial dentures with the use of resilient TSA (Titan Shock Absorber, BoneCare GmbH, Augsburg, Germany) abutment and conventional non-resilient abutment using finite element method. Methods This study presents two basic 3D models. For one model a standard non-resilient abutment is used, and on the implant of the second model a resilient TSA abutment is applied. The virtual model contains drawn contours of tooth, mucous membranes, implant, cortical bones and spongiosa, abutment and suprastructure. The experiment used 500 N of vertical force, applied in three different cases of axial load. Calculations of von Mises equivalent stresses of the tooth root and periodontium, implants and peri-implant tissue were made. Results For the model to which a non-resilient abutment is applied, maximum stress values in all three cases are observed in the cortical part of the bone (maximum stress value of 49.7 MPa). Measurements of stress and deformation in the bone tissue in the model with application of the resilient TSA abutment demonstrated similar distribution; however, these values are many times lower than in the model with non-resilient TSA abutment (maximum stress value of 28.9 MPa). Conclusion Application of the resilient TSA abutment results in more equal distribution of stress and deformations in the bone tissue under vertical forces. These values are many times lower than in the model with the non-resilient abutment.Uvod Razlike u odgovoru zuba i implantata na opterećenje mogu imati za posledicu niz bioloških i tehničkih komplikacija u uslovima delovanja okluzalnih sila. Cilj rada Cilj ovog rada je da se analizira distribucija opterećenja kod mešovito nošenih mostova sa primenom rezilijentnog TSA abatmenta (Titan Shock Absorber, BoneCare GmbH Germany), kao i konvencionalnog nerezilijentnog abatmenta primenom metode konačnih elemenata (MKE). Metode rada U ovom radu napravljena su dva osnovna 3D modela. Na jednom implantatu i modelu korišćen je standardni nerezilijentni abatment, a na implantatu drugog modela korišćen je rezilijentni TSA abatment. Na virtuelnom modelu su modelirane konture zuba, PDL-a, sluzokože, implantata, kortikalne i spongiozne kosti, abatmenta i suprastrukture. U eksperimentu je korišćena vertikalna sila od 500 N, koja je primenjena u tri različita slučaja aksijalnog opterećenja. Metodom konačnih elemenata izračunavani su potom Fon Mizesovi ekvivalentni naponi u korenu zuba i parodoncijumu, implantatu i periimplantatnom tkivu. Rezultati Na modelu kod koga je primenjen nerezilijentni abatment, maksimalne vrednosti napona i deformacije u sva tri slučaja su registrovane u kortikalnom delu kosti oko zuba i implantata u zavisnosti od napadne tačke sile (maksimalan napon 49,7 MPa). Vrednosti napona i deformacija na modelu sa primenom rezilijentnog TSA abatmenta pokazale su sličnu raspodelu u kosti, međutim ove vrednosti su višestruko manje nego kod modela sa nerezilijentnim abatmentom (maksimalan napon 28,9 MPa). Zaključak Primena rezilijentnog TSA abatmenta dovodi do ravnomernije raspodele napona i deformacije u koštanom tkivu oko zuba i implantata pod dejstvom vertikalnih sila. Izmerene vrednosti su višestruko manje nego na modelu sa nerezilijentnim abatmentom