GEOMETRICALLY NONLINEAR ANALYSIS OF PIEZOELECTRIC ACTIVE LAMINATED SHELLS BY MEANS OF ISOGEOMETRIC FE FORMULATION

The topic of piezoelectric active thin-walled structures has attracted a great deal of attention over the previous couple of decades. Lightweight structures with piezoelectric material based active elements, sensors and actuators, offer numerous advantages over their passive counterparts. This explains the motivation of authors to dedicate their work to this enticing research field. Accurate and reliable numerical tools for modeling and simulation of this type of structures is still a hot topic in the research community. This paper offers an isogeometric finite element formulation for shell type of structures made of composite laminates including piezoelectric layers characterized by the electro-mechanical coupling. The shell kinematics is based on the Mindlin-Reissner assumptions, thus including the transverse shear effects. A few examples selected from the available literature are considered to demonstrate the applicability of the developed numerical tool and assess its performance

Radiographic cephalometry assessment of the linear and angular parameters on cranial base in children with skeletal class III

Background/Aim. In malocclusion of skeletal class III, mandible is located in front of maxilla in sagital plain, which is manifested by a lower value of the sagital inter-jaw angle than in skeletal class I, where the jaw sagital relation is normal. Apart from the deformities on mandible and/or maxilla, in skeletal class III deformities are also frequent on the cranial base. The aim of this research was to find the differences in the parameter values on the cranial base among the children with skeletal class III and the children with skeletal class I in the period of mixed dentition. Methods. After clinical examination and orthopan-tomography, profile radiography of the head was analyzed in 60 examinees, aged from 6−12 years. The examinees were divided into two groups: group 1 - the children with skeletal class III; group 2 - the children with skeletal class I. Both linear and angular parameters on the cranial base were measured, as well as the angles of maxillary and mandible prognatism and the angle of sagital inter-jaw relation. The level of difference in the parameter values between the groups was estimated and the degree of correlation of the main angle of the cranial base with the angles of sagital position of the jaws in each of the two groups was established. Results. A significant difference between the groups was found only in the average values of the angles of maxillary prognatism and sagital interjaw relation. In the group 1, the main angle of the cranial base was in a significant correlation with the angles of sagital positions of the jaws, while in the group 2, such significance was not found. Conclusion. There were no significant differences in the parameter values on the cranial base between the groups. There was a significant correlation of the main angle of the cranial base with the angles of sagital position of the jaws in the group 1 only.

Razvoj izogeometrijske metode konačnih elemenata i njena primena u strukturnoj analizi nosećih struktura transportnih mašina

The subject of doctoral dissertation is the isogeometric structural analysis. The isogeometric analysis represents a special approach in the finite element method (FEM) which aims at closing the gap between the actual geometry of modeled structures and the geometry generated upon the finite element discretization. In the isogeometric FE analysis, NURBS (non-uniform rational basis spline) functions usually form the basis for the definition of both the geometric models and interpolation functions of the FE models. Regardless of the mesh density, the geometry is exactly described in the FE model. The aim of the dissertation is the systematization of procedures and methods necessary for isogeometric analysis by creating general mathematical forms and program procedures. Isogeometric FE models are defined by using the NURBS and T-spline basis functions. An isogeometric solid element is formulated as well as a Kirchhoff-Love shell element with the NURBS basic functions. The method of modeling complex structures formed from several surfaces by using Kirchhoff-Love elements is presented. The results of the performed isogeometric analyses were compared with analytical results, the results yielded by the classical finite element method and experimental results. The developed isogeometric models were tested in the field of linear static, modal and explicit dynamic analyses. A particular part of the dissertation is dedicated to the benefits of isogeometric analysis in the field of structural analysis of transport machines complex structures. The conclusions related to advantages and disadvantages of NURBS ant Tsplines basis functions in the finite element method are presented through examples and tests done in this dissertation. The directions of further research are proposed

ISOGEOMETRIC FE ANALYSIS OF COMPLEX THIN-WALLED STRUCTURES

Isogeometric analysis, as a special field of the finite element method (FEM) which integrates geometric and finite element mesh modelling, is one of the promising directions of FEM development. The paper presents a concept of isogeometric FEM analysis of thin-walled structures based on the Kirchhoff-Love shell formulation and NURBS as basis functions. The basic properties of isogeometric shell model are briefly given by means of NURBS interpolation functions. The problem of setting up larger models that involve multiple patches and their interconnection is addressed. Academic models as well as practical models from the field of heavy construction equipment demonstrate the applicability of developed tools for static FEM analysis

Orthodontic Treatment of Dentofacial Deformities

Međučeljusni nesklad stvara velike probleme pacijentima i estetski i funkcionalno. Razlog dolaska pacijenata u Kliniku uglavnom je estetske naravi, jer se radi o mlađim osobama, a funkicionalne su smjetnje u drugome planu. Uzimanje hrane, govor i disanje u takvih su osoba znatno otežani. Prikazat ćemo jedan od slučajeva liječenje kombiniranoga dentofacijalnog deformiteta: PROGNATHISMUS ET LATEROGNATHISMUS MANDIBULARIS. Pacijentica, 34 godine. Iz anamnestičkih podataka nismo saznali da sličnih problema ima u obitelji. Motiv dolaska na Kliniku bio je estetske naravi, premda se je pacijentica žalila na bolove u oba čeljusna zgloba, otežano uzimanje hrane i na nešto teži izgovor pojedinih glasova. Plan liječenja donesen je na osnovi sljedećih potanko provedenih postupaka: • raščlamba lica rađena je na osnovi fotogarafija napravljenih iz profila i en face • raščlamba okluzije učinjena je na studijskim modelima • rentgenkefalometrijska raščlamba profilnog i AP kraniograma učinjena računalom i ručno samo je potvrdila već spomenutu dijagnozu Liječenje je provedeno isključivo intraoralnom i ekstraoralnim ortodontskim napravama te smo smatrali korisnim iznijeti naša iskustva ovakvim načinom liječenja. Izgled pacijentice nakon liječenja vidi se na slikama. Ponovne kefalometrijske raščlambe rađene su nakon završetka liječenja. Svi parametri su u granicama normale, kako se vidi iz tabele s prikazanim vrijednostima prije i poslije liječenja. Raščlambe mekih česti pacijentice također pokazuju znatne promjene, a odnosi nos, gornja usnica, donja usnica i brada veoma su dobri. Dentofacijalni deformiteti danas se vrlo uspješno rješavaju. Dobre studijske raščlambe, na osnovi kojih se određuje plan liječenja, jamstvo su uspješnoga liječenja. Vrlo malo je ostalo tajni u liječenju dentofacijalnih deformiteta, ali ona od terapeuta traži visoku profesionalnost i učinkovitost.Disharmony of the jaws presents a great aesthetic and functional problem for patients. The reason for reporting to a clinic is mainly of an aesthetic nature, since most commonly young people are involved, while functional disturbances remain secondary. Such persons have difficulty eating, speaking and breathing. We will present one case of combined dentofacial deformity: PROGNATHISMUS ET LATEROGNATHISMUS MANDIBULARIS. Female patient, 34 years old. From anamnestic data we did not find out whether there were similar problems in the family. The motive for reporting to the clinic was aesthetics, although the patient complained of pain in both temporomandibular joints, difficulty eating and somewhat more difficult pronunciation of certain vocals. A treatment plan was based on: • Analysis of the face, based on profile and en face photographs. • Analysis of occlusion, based on study models. • Roentgen-cephalometry of the profile and AP craniogram, performed on a computer as well as manually, confirmed the above mentioned diagnosis. The treatment was performed exclusively with intraoral and extraoral orthodontic appliances, and we therefore believe that it would be useful to present our experience with such a treatment method. The appearance of the patient after treatment can be seen on the photographs. Repeated cephalometric analyses were performed after completion of the treatment. All parameters were within normal limits, as can be seen from the table presenting pre- and post treatment values. Analysis of the soft tissues also shows significant changes, and relations between the nose, upper lip, lower lip and chin are very good. Today dentofacial deformities are successfully solved. Good study analyses, which serve as the base for planning treatment, guarantee successful treatment. There are very few secrets in ortognatic treatment, but it still requires high professionalism and effectivness

ISOGEOMETRIC STRUCTURAL ANALYSIS BASED ON NURBS SHAPE FUNCTIONS

Finite element method (FEM) is a tool that is mostly used for the structural analysis. The method is based upon approximation of the actual geometry and displacement field of the structure over the finite element domain.  In practice, Lagrange polynomials are mostly used as shape functions (approximate functions). They provide only the C0-continuity at the element boundaries. This paper elucidates a possible approach based on the so-called isogeometric analysis to improve this property. The isogeometric FEM analysis applies the same functions to describe the CAD model, the element geometry and the element displacements. The paper represents developed algorithm and the obtained results for a relatively simple test case

Orthognathic Surgery - Our Concept

Ortognatska kirurgija spada u skupinu estetsko-funkcionalnih operacija. Većina naših bolesnika dolazi na prvi pregled zahtijevajući promjenu izgleda. Prvi pregled je razgovor s bolesnikom i na njemu se uvijek nazočni ortodont i maksilofacijalni kirurg. Uzimaju se otisci fotografija an face i profila te telerendgen snimke. Na osnovi dobivenih podataka stvara se okvirni plan liječenja. Na drugome pregledu iznosi se plan liječenja i potanko se objašnjavaju postupci ortodontskog i kirurškog liječenja i moguće komplikacije. U razgovoru se rabi baza podataka ortognatskih zahvata i računalna simulacija. Bolesnici donose konačnu odluku te se na trećemu pregledu dogovara liječenje. Aktivno liječenje rijetko počinjemo prije sedamnaeste godine. Ovisno o planu, uključuje se oralni kirurg i počinje se s ortodontskim tretmanom. Kada je priprema za zahvat završena, ponavlja se razgovor s bolesnikom i dogovara se termin primitka. Bolesnik dolazi na bolničko liječenje pripremljen i s obavljenim anesteziološkim pregledom. Operacija je najčešće na dan primitka, a bolesnik u bolnici boravi 3 do 5 dana. Na primjerima vraćanja i izvlačenja donje i gornje čeljusti te bimaksilarnih zahvata prikazati ćemo naš pristup ortognatskoj kirurgiji.Orthognathic surgical treatment is both functional and esthetic. For most of our patients the reason for the first visit is esthetics. The first appointment is made in the combined maxillofacial and orthodontics clinic. During the first appointment we talk to the patient to get a general idea of his/her wishes and medical photographs, jaw models and X-rays are taken. After collecting all data a general plan for the treatment is made. During the second appointment we discuss our treatment plan together with details of both orthodontic and surgical therapy with the patient. In this discussion we use photographs from our data base and computer simulation. After the final patient’s decision is made, we start with the treatment. Depending on the treatment plan, it starts with either oral surgery or orthodontics. For most of the patients we do not start with treatment before seventeen years of age. After presurgical treatment is finished, we again discuss details of the operation with the patient and a hospital appointment is made. The operation is usually performed on the day of admission, and the hospital stay is 3 to 5 days. We discuss our treatment concept based on patients with the different types of skeletal deformities

Cephalometric assessment of maxillary length in Serbian children with skeletal class III

Background/Aim. Malocclusion of skeletal class III is a complex irregularity of sagittal inter-jaw relationship, which is due to irregularities of sagittal position of one or both of the jaw bones, which is often associated with disproportionate ratio of their length. The aim of this study was to determine whether the length of the jaw of children with skeletal class III in the period of mixed dentition was changed. Methods. Fifty children with skeletal class III and the same number of those with skeletal class I, of both sexes, have been selected on the basis of cephalometric analysis of profile tele-x-ray of the head. All the children aged 6-12 had mixed dentition, and were divided according to sex and age into three subgroups within each group. The length of maxilla, mandible and cranial base were measured. Proportions among the lengths measured within each group were found and difference significance in the measured lengths and their proportions among groups and subgroups were evaluated. Results. The children with skeletal class III, compared with the findings in the control group, had significantly lower values of maxillary length, total maxillary length, as well as lower values of their lengths in proportion to lengths of the front or the total length of cranial base and in proportion to mandibular lengths (p < 0.05). Among the patients of different sexes, both in the test and the control group, a significant difference in the values of the measured lengths was found. Conclusion. The children with skeletal class III have significantly shorter maxilla than those with skeletal class I

Optimization of the flue gas-flow controlling devices of the electrostatic precipitator of unit A4 in TPP "Nikola Tesla"

Homogeneity of the flue gas-flow through the chamber of an electrostatic precipitator is one of the basic influencing parameter on dedusting efficiency. This paper presents results of a multiobjective optimization study of the flue gas controlling devices of electrostatic precipitator of 324 MWe lignite fired Unit A4 of TPP "Nikola Tesla" in Serbia. The aim was to achieve better flow homogeneity in the cross-section of the precipitator compared to the original design. Additional constraints were to maintain the minimum as possible overall weight of the proposed design as well as pressure drop through the precipitator. Numerical simulations based on CFD were used to investigate dependence of the velocity distribution in the ducts and precipitator’s chamber with respect to the geometrical parameters of tested concepts of turning blades. A series of 22 detailed full-scale numerical models of the precipitator with different concepts of turning vanes designs were developed. Assessment of the flow field uniformity for each tested design was performed based on the analysis of several homogeneity parameters calculated for selected vertical cross-sections of the precipitator. After the reconstruction according to optimized design, results of measurements confirmed significant improvements of the velocity distribution in the vertical cross-sections of the precipitator, increase of dedusting efficiency and reduction of PM emission

Serbia: Another endemic region for canine ocular thelaziosis

Canine thelaziosis is widely distributed in Far Eastern countries and considered endemic in many European countries, between latitudes 39 and 46 N. Because of the unique relationship between the causer and its intermediate and final hosts, the genus Thelazia is one of the most specialized nematodes in the taxon. Thelazia callipaeda (superfamily: Thelazioidea) infects the conjunctivas of several mammalians, including dogs and humans. Since dogs may also represent a reservoir of infection for humans, the aim of the study was to show the epidemiological situation of thelaziosis in dogs in the Republic of Serbia, after it was first diagnosed in 2014, which is crucial for the successful treatment, control, and prevention of the disease. The research was performed on privately owned dogs in the period from the end of April 2013 to the end of October 2015 in 7 different regions in Serbia. Adult parasites were mechanically removed from dogs with manifested ocular disorders, and thelaziosis was diagnosed in 178 out of 501 animals. The high prevalence of T. callipaeda in dogs (35.52%) in the analyzed areas of Serbia indicates the endemicity of eyeworm infestation in these areas