Modelovanje fokalno-direktrisnih površi za primenu u arhitekturi

The theme of this paper is the modeling of focal-directorial surfaces, starting with their definition, as a locus of points, whose sum of the distances to the focus and/or directrix is constant and predefined. We presented a heuristic algorithm for modeling surfaces and their isocurves, achieved through the use of the Grasshopper visual programming editor in the RhinoCeros environment. Surfaces and their isocurves were generated in a spherical grid, because a Cartesian grid proved unsuitable for the task and the chosen approach. This paper additionally proposes a modeling algorithm of a discrete variation of focal-directorial surfaces. The proposed modeling method is a 3D convex hull implemented on a set of surface points, with the selected points close to that surface. The discrete model is realized both in a Cartesian and spherical grid. There are significant differences between the obtained results.Tema ovog rada je modelovanje fokalno-direktrisnih površi polazeći od njihove definicije, kao geometrijskog mesta tačaka čiji je zbir rastojanja do fokusa i/ili direktrisa konstantan i unapred zadat. Predložen je jedan heuristički algoritam za modelovanje površi i njihovih izolinija koji je realizovan pomoću vizuelnog grafičkog editora Grasshoper u RhinoCeros okruženju. Generisanje površi i njihovih izolinija realizovano je u sfernom gridu, pravougli grid se pokazao kao nepodesan za postavljeni zadatak i pristup. U ovom radu je, dodatno, predložen i algoritam modelovanja diskretne varijante fokalno-direktrisnih površi. Kao način modelovanja, predložen je 3D convex hull primenjen na skupu tačaka površi i izabranih tačaka bliskih toj površi. Diskretni model je realizovan u pravouglom, i u sfernom gridu. Dobijeni su rezultati koji se značajno međusobno razlikuju

Parametri kvaliteta suncokretovog ulja i palminog oleina tokom višestrukog prženja

The refined sunflower and palm oils are used in the food industry for the production of fried potatoes. Literary data have shown that palm oil had less tendency to degradation than sunflower oil due to its fatty acid composition. However, palm olein is a palm oil fraction and therefore has a different composition of fatty acids. The aim of this study was to investigate the quality of the refined palm olein in relation to the refined linoleic type sunflower oil during the production of fried potatoes. The oil samples were used for multiple frying during the seven days (40 minutes per day at a temperature of 165o C). The peroxide value and free fatty acid content (acid value) were determined by standard analytical methods. The results showed that the peroxide value in sunflower oil and palm olein increased by 75.0% and 77.8%, while the acid value increased by 50.0% and 26.8%, respectively, in relation to their initial values in the fresh oil samples. Based on these results, it can be concluded that the palm olein was more suitable for frying. However, this finding cannot be reported with certainty because the quality of the oil depends on many more parameters, not only on those analysed in this paper.U prehrambenoj industriji se za proizvodnju prženog krompira koriste rafinisano suncokretovo i palmino ulje. Prema literaturnim podacima, palmino ulje ima manju sklonost ka degradacionim promenama u odnosu na suncokretovo ulje, zahvaljujući sastavu masnih kiselina. Međutim, palmin olein je frakcija palminog ulja i samim tim ima drugačiji sastav masnih kiselina. Cilj ovog rada bio je da se ispita kvalitet rafinisanog palminog oleina u odnosu na rafinisano suncokretovo ulje tokom proizvodnje prženog krompira. Uzorci ulja su korišćeni za višestruko prženje tokom sedam dana (po 40 minuta svakog dana, na temperaturi od 165o C). Peroksidni broj i sadržaj slobodnih masnih kiselina (kiselinski broj) određeni su standardnim analitičkim metodama. Rezultati su pokazali da se peroksidni broj u suncokretovom ulju i palminom oleinu povećao 75,0% odnosno 77,8%, dok se kiselinski broj povećao 50,0% odnosno 26,8%, u odnosu na početne vrednosti u uzorcima svežeg ulja. Na osnovu ovih rezultata može se zaključiti da je palmin olein pogodniji za prženje. Međutim, ovaj zaključak se ne može navesti sa sigurnošću jer kvalitet ulja zavisi od mnogo više parametara, a ne samo od onih analiziranih u ovom radu

Proizvodnja goveđeg mesa obogaćenog organski vezanim selenom

In this study, the effects of the organic and inorganic form of selenium, in the diet for finishing beef cattle, were investigated. Sell-Plex produced by American firm Alltech as a source of organic selenium with selenium concentration of 2000 mg/kg was used. The source of inorganic selenium was sodium selenite. The trial was conducted on Simmental fattening cattle in the final stage in the free housing system and it lasted 60 days. Selenium content in control and trial group (m. longissimus dorsi) was 78.65 and 125.03 μg/kg (P (lt) 0.01), in kidneys 855.52 and 1026.04 μg/kg(P (lt) 0.001); in liver 453.13 and 534.64 μg/ kg(P (lt) 0.01) and in spleen 308.44 and 383.62 μg/kg (P (lt) 0.001), respectively. There were no differences in main carcass characteristics, share of some tissues in the round and three rib chops, chemical composition and meat quality of m. longissimus dorsi (P>0.05).Considering the higher storage of organic selenium in meat and internal organs of the fattening cattle with respect to the inorganic form, it was concluded that the selenium supply in organic form has a better bioavailability. Inclusion of organic selenium into the diet in the final stage of fattening cattle and its deposition in meat and internal organs is a good and easy way to get meat with functional foods properties that in addition to nutritional value should positively affect human health.U radu su ispitani efekti organskog i neorganskog selena u obrocima junadi u tovu. Kao ozvor organskog selena korišćen je preparat Sell-Plex u kome je koncentracija selena iznosila 2000 mg/kg a izvor neorganskog selena bio je natrijumselenit. Ogled je izveden na Simentalskoj rasi goveda u završnoj fazi tova u slobodnom sistemu držanja i trajao je 60 dana. Sadržaj selena u m. longissimus dorsi, jetri, slezini i bubrezima bio je značajno viši na ishranbenom tretmanu sa organskim selenom u odnosu na neorganski, što ukazuje na njegovu bolju bioiskoristivost. Urađena je disekcija polutke prema zvanično važećoj skali za klasifikaciju trupova odraslih goveda propisanoj od strane evropske zajednice. Dobijeni rezultati ukazuju da nije bilo razlike između tretmana sa organskim i neorganskim selenom u telesnoj masi grla pre klanja kao i glavnim karakteristikama polutke. Takođe, nije bilo razlike u udelu pojedinih tkiva u butu i trorebarnom isečku kao i ni u hemijskom sastavu i kvalitetu mesa u m. longissimus dorsi. Imajući u vidu da je selen esencijalan mikroelement u ishrani a da organski vezan selen ima bolju bioiskoristivost u odnosu na neorganski, njegovo uključivanje u obroke goveda i deponovanje u mesu i unutrašnjim organima je dobar i jednostavan način za dobijanje mesa sa svojstvima funkcionalne hrane koja treba da pored nutritivne vrednosti pozitivno utiče na zdravlje ljudi. Pošto su pojedini delovi planete Zemlje slabo opskrbljeni sa selenom ovo je najjednostavniji način da se reši problem njegovog deficita

Proračun posuda sa vazduhom za zaštitu cevovoda od hidrauličnog udara

Posude sa komprimovanim vazduhom mogu na efektivan način da umanje pojavu prekomernog povišenja i smanjenja pritiska usled hidrauličnog udara u industrijskim cevovodima. U radu je prikazana pojednostavljena procedura za proračun zapremine posude koju zauzima vazduh i ukupne zapremine posude. U radu su date preporuke za pravilan izbor dimenzija ulaznog i izlaznog cevnog priključka na posudi čime se može minimizirati njena zapremina

Changes in Traditional Activities of Industrial Area toward Sustainable Tourism Development

The purpose of this study is to investigate the potential for restructuring industrial areas toward tourism development within local communities, with a special emphasis on the socio-cultural determinants of residents, as well as their attitudes regarding the sustainable development of tourism. The research is also oriented toward the interests of local communities with respect to entrepreneurial activities in the field of tourism within regions relying on traditional industries, in this case, one of the largest open-pit mining surfaces in Europe (near the Serbian town of Lazarevac). The survey was conducted on a sample of 273 respondents. The research results point to the residents’ attitudes regarding the acceptability of tourism development options, as well as their attitudes toward tourism development, with the aim of providing the conditions for a successful transition from a typical heavy industrial setting toward sustainable tourism development

Просторна и вертикална дистрибуција Cs137 у земљишту Србије

U ovom radu prikazane su specifične aktivnosti 137Cs u zemljištu Srbije u periodu od 2006. do 2014. godine. Predstavljena je prostorna distribucija ovog radionuklida, distribucija po dubini zemljišnog profila za različite tipove zemljišta i veza sa fizičko-hemijskim karakteristikama zemljišta. Ovi rezultati daju uvid u glavne faktore koji utiču na migraciju 137Cs u zemljištu, što doprinosi saznanjima o ponašanju ovog radionuklida u životnoj sredini i faktorima koji regulišu njegovu mobilnost unutar kopnenih ekosistema.In this study the specific activities of 137Cs were determined in the soil of Serbia in the period from 2006 to 2014. The spatial and vertical distribution of 137Cs in the soil profiles of different soil types and its relationships with the physico-chemical soil properties were analyzed. The obtained results provide insight into the key factors influencing the migration of 137Cs in the soil, which contributes to knowledge of its behavior in the environment and the factors affecting its mobility within terrestrial ecosystems.Article is part of: [http://vinar.vin.bg.ac.rs/handle/123456789/8230

The distribution of the mass concentrations of potassium, thorium and uranium in soils from the territories of the cities of Serbia

U radu su prikazane masene koncentracije kalijuma, torijuma i uranijuma u uzorcima zemljišta sa teritorija 16 većih gradova Srbije sakupljenih u periodu od 2003. do 2015. godine, izračunate na osnovu gamaspektrometrijski izmerenih aktivnosti ovih radionuklida. Srednje vrednosti koncentracija analiziranih elemenata u uzorcima zemljišta iznose za kalijum 1,6% (od 0,5 do 2,6%), torijum 8,7 mg/kg (od 2,4 do 15,1 mg/kg) i uranijum 2,6 mg/kg (od 0,8 do 4,7 mg/kg). Masene koncentracije kalijuma, torijuma i uranijuma u analiziranim zemljištima pokazuju normalnu raspodelu. Analizirana je međusobna zavisnost parova radionuklida i dobijeni su Pirsonovi koeficijenti korelacije od 0,88 za K/Th, 0,89 za K/U i 0,98 za Th/U.In this study, the mass concentrations of potassium, thorium and uraniuminsoils collected from the territories of 16 cities of Serbia collected in the period 2003-2015, were calculated based on specific activities of these radionuclides measured by gamma-ray spectrometry. The mean values of elemental mass concentrations in analyzed soil samples were found to be 1.6% for K, 8.7 mg/kg for Th and 2.6 mg/kg for U. The mass concentration of potassium, thorium and uranium in analyzed soils follows normal distribution. The relationshipsbetween pairs of radionuclides were analyzed and obtained Pearson correlation coefficientsof were 0.88 for K/Th, 0.89 for K/U and 0.98 for Th/U

PZT-NZF/CF ferrite flexible thick films: Structural, dielectric, ferroelectric, and magnetic characterization

The preparation and properties of thick flexible three-phase composite films based on lead zirconium titanate (PZT) and various ferrites (nickel zinc ferrite (NZF) and cobalt ferrite (CF)) were reported in this study. Properties of three-phase composite films were compared with pure polyvinylidene fluoride (PVDF) and PZT-PVDF films. X-ray diffraction data indicated the formation of well crystallized structure of PZT and NZF/CF phases, without the presence of undesirable phases. Scanning electron micrographs showed that the ceramic particles were dispersed homogeneously in the PVDF matrix and atomic force microscopy confirmed that the size of the particles is around 30 nm. Non-saturated hysteresis loops were evident in all samples due to the presence of highly conductive ferrite phases. Under magnetic field of 10 kOe, composite films exhibited a typical ferromagnetic response. Dielectric properties were investigated in the temperature range from -128 to 250 degrees C and frequency range of 400 Hz-1 MHz. The results showed that the value of dielectric constant of the PVDF/PZT/ferrite composites increased about 25% above the one obtained for pure PVDF

Effects of three types of physical activity on reduction of metabolic parameters involved in cardiovascular risk

The aim of present study was to investigate the effects of three different types of physical activity on reduction of the metabolic parameters mainly responsible for cardiovascular diseases. This prospective-intervention study was performed at the 'ČIGOTA' Thyroid Institute on Mt. Zlatibor (Serbia) between August 2004 and June 2006. Sixty-eight overweight/obese patients aged 40-70 years with hyperlipidemia were divided into three groups according to their weight and overall health. The program of physical workout included: group I - fast walking; group II - gymnastic exercises and specially chosen exercises in the swimming pool; and group III - combined physical training of higher intensity and greater length. All patients were also on a special reduced diet of 1000 kcal per day, the AHA step-2 diet. We monitored the body mass index, body composition, glucose, cholesterol (total, LDL-, and HDL-), and triglycerides before, during, and after the intervention. After 2 and particularly 12 weeks of intervention, a significant improvement of all metabolic parameters was achieved in all three groups of patients. Although most patients completed the study with normal values of all parameters, the most desirable results were achieved in group III (combined exercises with an average energy expenditure of 900 kcal per day). Our research indicates that a specially conceived program of physical activity and diet intervention resulted in significant reduction of cardiovascular risk factors