Descriptive-geometrical methods in computer graphics: intersection between two surfaces of revolution by use of common spheres and common planes

U disertaciji je razmatrana problematika određivanja intersekcije dveju rotacionih površi. Ovo je izvedeno u petnaest poglavlja. U prvom poglavlju (Uvod) istaknuta je potreba da se presek dveju rotacionih površi određuje korišćenjem metoda koji u osnovi imaju deskriptivno geometrijski pristup. Takođe je dat pregled celog rada i kroz dijagrame je sistemcitizovana strategija za postcivku i rešavanje problema. U drugom poglavlju (Određivanje preseka površi u komjuterskoj grafici) izvršena je analiza postojećih metoda za određivanje međusobnog preseka dveju površi i uočeni su izvesni nedostaci ovih postupaka.U trećem poglavlju (Projiciranje) određena je dvodimenzionalna slika trodimenzionalnog objekta u slučajevima paralelnog i centralnog projiciranja. U četvrtom poglavlju (Kontura rotacione površi) određene su trodimenzionalne koordinate tačaka na konturi rotacione površi za oba slučaja projiciranja. U petom poglavlju (Pomoćne ravni) prikazani su matematički modeli za određivanje trodimenzionalnih koordinata tačaka prostorne presečne krive dveju rotacionih površi za tri slučaja međusobnog odnosa osa dveju rotacionih površi: ose su paralelne, seku se ili se mimoilaze. Za rešavanje problema korišćene su pomoćne ravni. U šestom poglavlju (Pomoćne lopte) korišćene su pomoćne lopte i za tri slučaja u odnosima između osa dveju rotacionih površi su formirani matematički modeli za određivanje prostorne presečene krive dveju površi. U sedmom poglavlju (Transformacije) izdvojene su ključne dvodimenzionalne i trodimenzionalne transformacije. U osmom poglavlju (Osnovna tela i njihovi odnosi) analizirana su osnovna geometrijska tela poput kocke, paralelopipeda, cilindra i lopte. Prikazani su načini za zadavanje ovih tela kao i procedure za definisanje međusobnog odnosa dva tela. U devetom poglavlju (Ravne krive u kompjuterskoj grafici) analizirane su najfrekventnije ravne krive u kompjuterskoj grafici koje se kao polazni objekti često koriste za generisanje površi. U desetom poglavlju (Površi u kompjuterskoj grafici) prikazani su različiti postupci za dobijanje površi u kompjuterskoj grafici. U jedanaestom poglavlju (Pregled aktuelnog softvera) prikazane su mogućnosti softvera za dobijanje površi i određivanje njihovog uzajamnog preseka. U dvanaestom poglavlju (Rezultati) prikazane su slike-rezultati koje reprezentuju dobre osobine formiranih matematičkih modela. U trinaestom poglavlju (Zaključak) analizirani su dobijeni rezultati i mogućnost daljeg istraživanja na istom ili sličnim problemima. U četrnaestom poglavlju (Literatura) navedene su knjige i naučni radovi koji su citirani i korišćeni tokom izrade disertacije. U petnaestom poglavlju (Prilog-listing programa) prikazan je listing Pascal programa.In the dissertation the problem of intersection between two surfaces of revolution has been considered. The subject has been presented in fifteen sections. In the first section (Introduction) the need for determination of intersecting curve between two surfaces of revolution by use of methods based on descriptive geometrical access has been underlined. The dissertation review has been given and the strategy for formulation and determination of problems by use of diagrams has been systematised. In the second section (Interseclions of surfaces in computer graphic) former approaches for surface-surface intersection have been analysed and several shortages have been noted. In the third section (Projection) the two-dimensional picture of three-dimensional object in cases of parallel and central projections has been determined. In the fourth section (Contour lines of surface of revolution) the three-dimensional point ’s coordinates on contour lines of surface of revolution for both projection cases have been solved. In the fifth section (Common planes) the mathematical models for determination three-dimensional point 's coordinates of space intersecting curve between two surfaces of revolution have been presented. Three different cases have been considered: axes of surfaces of revolution are parallel, axes are intersecting or pass each other. For determination of problem common planes have been used. In the sixth section (Common spheres) common spheres have been used. The mathematical models for determination intersecting space curve for three different cases in relations behveen axes of surfaces of revolution have been formed. In the sixth section (Common spheres) common spheres have been used. The mathematical models for determination intersecting space curve for three different cases in relations behveen axes of surfaces of revolution have been formed. In the seventh section (Transformations) the basic two-dimensional and three-dimensional transformations have been presenled. In the eighth section (Basic solids and their relations) the basic solids: cube, block, cylinder and sphere have been analysed. The assign solids ways and procedures for determination of relation between two solids have been analysed. In the ninth section (Plane curves in computer graphic) the most frequent plane curves in computer graphic which often used for determination of surfaces like starting objects have been analysed. In the tenth section (Surfaces in computer graphics) the different procedures for determination of surfaces in computer graphics have been presented. In the eleventh section (Pascal program review) the actual softwares possibilities for determination of surfaces and their intersections have been presented. In the twelfth section (Results) the pictures-results which represented good features of formed mathematical models have been presented. In the thirteenth section (Conclusion) the obtained results have been analysed as well as the possibilities of further investigations for both same and similar problems. In the fourteenth section (References) books and scientific papers, which have been either quoted or used in this dissertation, have been given. In the fifteenth section (Additional list-Program listing) the used Pascal program has been presented

Designs of solar concentrators

Ovaj rad daje uvid u dizajn koncentrisanih solarnih sistema (CSP). Prikazano je nekoliko tipova već postojećih sistema sa njihovim prednostima i manama. Ove prednosti i mane su bazirane prilikom upotrebe ovih sistema kao i njihovim konstruktivnim karakteristikama i ovaj rad daje preporuku za odabir najpogodniji sistem. Nakon prezentacije ovih tipova CSP sistema dat je prikaz novog dizajna solarnog koncentratora koji je nastao kao kombinacija nekoliko različitih tipova solarnih koncentratora.This paper gives an insight into the design of concentrating solar power (CSP) systems. The basic design of several types of CSP system is presented alongside their advantages and disadvantages. These advantages and disadvantages are based on their application and construction details and the paper shows how to select the most convenient CSP system. After presenting these types of CSP systems, an example of a new type of design is explained that presents a combination of several other solar concentrators

Designs of solar concentrators

Ovaj rad daje uvid u dizajn koncentrisanih solarnih sistema (CSP). Prikazano je nekoliko tipova već postojećih sistema sa njihovim prednostima i manama. Ove prednosti i mane su bazirane prilikom upotrebe ovih sistema kao i njihovim konstruktivnim karakteristikama i ovaj rad daje preporuku za odabir najpogodniji sistem. Nakon prezentacije ovih tipova CSP sistema dat je prikaz novog dizajna solarnog koncentratora koji je nastao kao kombinacija nekoliko različitih tipova solarnih koncentratora.This paper gives an insight into the design of concentrating solar power (CSP) systems. The basic design of several types of CSP system is presented alongside their advantages and disadvantages. These advantages and disadvantages are based on their application and construction details and the paper shows how to select the most convenient CSP system. After presenting these types of CSP systems, an example of a new type of design is explained that presents a combination of several other solar concentrators

Copyright Protection of 3D Digitized Sculptures by Use of Haptic Device for Adding Local-Imperceptible Bumps

This research aims to improve some approaches for protecting digitized 3D models of cultural heritage objects such as the approach shown in the authors\u27 previous research on this topic. This technique can be used to protect works of art such as 3D models of sculptures, pottery, and 3D digital characters for animated film and gaming. It can also be used to preserve architectural heritage. In the research presented here adding protection to the scanned 3D model of the original sculpture was achieved using the digital sculpting technique with a haptic device. The original 3D model and the model with added protection were after that printed at the 3D printer, and then such 3D printed models were scanned. In order to measure the thickness of added protection, the original 3D model and the model with added protection were compared. Also, two scanned models of the printed sculptures were compared to define the amount of added material. The thickness of the added protection is up to 2 mm, whereas the highest difference detected between a matching scan of the original sculpture (or protected 3D model) and a scan of its printed version (or scan of the protected printed version) is about 1 mm

Seizmička analiza fleksibilnih ukopanih potpornih konstrukcija prema različitim tehničkim normativima

Prikazane su odredbe vezane za projektovanje fleksibilnih ukopanih potpornih zidova na dejstvo zemljotresa za tri izabrana seizmička propisa – Evrokod 8, nacrta Pravilnika o tehničkim normativima za projektovanje i proračun inženjerskih objekata u seizmičkim područjima iz 1986. godine i prema odredbama američkih propisa AASHTO za seizmički proračun potpornih konstrukcija iz 2009. godine. Na primeru jednostavne ukopane nepoduprte potporne konstrukcije izvedene u krupnozrnom tlu izvršena je uporedna analiza seizmičkog proračuna primenjući dva numericka postupka prema nabrojanim propisa. Određeni su seizmički pritisci tla, potrebne dubine ukopavanja, kao i pomeranja. Iz rezultata proračuna izvedeni su zaključci i date preporuke za analizu ovog tipa potpornih konstrukcija na dejstvo zemljotresa

A quality of life assessment and the correlation between generic and disease-specific questionnaires scores in outpatients with chronic liver disease-pilot study

Introduction. Chronic liver diseases (CLD) are an important cause of morbidity and mortality in general population. The aim of this study was to analyze potential differences between patients with CLD and healthy control group, and to estimate the severity of CLD by using simple questionnaires: general health questionnaire (GHQ-12) and chronic liver disease questionnaire (CLDQ). Methods. A cross-sectional pilot study was performed in Zemun Clinical Hospital during years 2014 and 2015. Sixty participants were divided into 4 groups (15 per group): chronic alcoholic hepatitis, other chronic hepatitis, liver cirrhosis, and healthy control group. Entire study population chose one of four offered answers of structured questionnaires GHQ-12 and CLDQ, based on which mean model of end-stage liver disease (MELD) and Child-Turcotte-Pugh (CTP) scores were calculated. Results. Mean GHQ12 and CLDQ scores were 10.5 and 5.21 +/- 1.11 respectively. Regarding certain CLDQ domain scores, a significant difference between alcoholic and non-alcoholic hepatitis groups in the worry domain was observed. Mean MELD score was 7.42 +/- 2.89 and did not differ between chronic hepatitis groups, while mean CTP score was 5.73 +/- 0.88. A statistically significant correlation was observed between GHQ12 and CLDQ scores (rho = -0.404, p LT 0.01), but not between subjective and objective scores. Conclusions. Mean GHQ12 and CLDQ scores pointed out to general psychological no-distress condition of the studied participants, as well as scarcely expressed CLD-specific complaints. Mean MELD and CTP scores indicated stable chronic liver diseases, with low three-month mortality rates in the cases of chronic hepatitis, as well as determination to Child A group in the case of liver cirrhosis

Non-alcoholic fatty liver disease: a multidisciplinary clinical practice approach—the institutional adaptation to existing Clinical Practice Guidelines

Non-alcoholic fatty liver disease (NAFLD) is among the most frequently encountered chronic liver diseases in everyday clinical practice. It is considered the hepatic manifestation of metabolic syndrome. Today, liver biopsy is still the gold standard for NAFLD confirmation and assessing NAFLD's possible progression to non-alcoholic steatohepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma. Because of the high prevalence of NAFLD and potential associated risks of invasive diagnostic procedures, it is of great interest to recruit the patients for liver biopsy. However, as the presence of liver fibrosis determines the further clinical course, liver biopsy is expectedly reserved for those with increased fibrosis risk. The quality of liver biopsy recruitment and patient monitoring could be significantly improved by using non-invasive tools to assess liver fibrosis presence and interactive collaboration between general practitioners, gastroenterologists, and endocrinologists. As a result, the quality of liver biopsy recruitment and patients monitoring could be significantly improved. Here, we proposed clinical practice guidelines that could be implemented for everyday clinical practice in NAFLD patients

RISK FACTORS AND BONE MINERAL DENSITY IN ATHLETES AND NON-ATHLETES

Risk factors are important aspects in the treatment of patients with lower bone mineral density (BMD).The objective of this study was to estimate the association between risk factors and BMD status of subjects.Forty subjects - athletes of first sub-sample, were recruited from a football club “Železničar” in Niš, while forty subjects - non-athletes of the second sub-sample, were recruited from the Faculty of Occupational Safety in Niš, totally 80 subjects of masculine sex. BMD was diagnosed by using Dual X-Ray Energy Absorptiometry (DEXA densitometer), in the lumbar region of the spinal column and region of the hip articulation, while the presence of risk factors was evaluated by the One-Minute Osteoporosis Risk Test, ie. questionnaire of the International Osteoporosis Foundation, just before the diagnostics of BMD. All subjects agreed with the terms of research, conducted in accordance with the Declaration of Helsinki.Among 80 subjects, in six (1 athlete and 5 non-athletes) athletes osteopenia was found in the lumbar region of the spinal column, and in three (non-athletes) osteopenia was found in the region of hip articulation. Based on the results of χ2 test, there was the association between the lack of physical activity as a risk factor and osteopenia in the lumbar region of the spinal column (BMDSPINE osteopenia), and between the lack of physical activity as a risk factor and osteopenia in the region of hip articulation (BMDHIP osteopenia), while the association significance between smoking as a risk factor and BMDSPINE osteopenia should be taken with caution, because it is approaching the critical value (p=0.056).Concerning this research, the risk factors had a considerably greater impact on low BMD in non-athletes, compared to athletes, ie., in patients who are smokers and lack physical activity