A numerical investigation of the solution of a class of fourth-order eigenvalue problems

This paper is concerned with the accurate numerical approximation of the spectral properties of the biharmonic operator on various domains in two dimensions. A number of analytic results concerning the eigenfunctions of this operator are summarized and their implications for numerical approximation are discussed. In particular, the asymptotic behaviour of the first eigenfunction is studied since it is known that this has an unbounded number of oscillations when approaching certain types of corners on domain boundaries. Recent computational results of Bjorstad & Tjostheim, using a highly accurate spectral Legendre-Galerkin method, have demonstrated that a number of these sign changes may be accurately computed on a square domain provided sufficient care is taken with the numerical method. We demonstrate that similar accuracy is also achieved using an unstructured finite-element solver which may be applied to problems on domains with arbitrary geometries. A number of results obtained from this mixed finite-element approach are then presented for a variety of domains. These include a family of circular sector regions, for which the oscillatory behaviour is studied as a function of the internal angle, and another family of (symmetric and non-convex) domains, for which the parity of the least eigenfunction is investigated. The paper not only verifies existing asymptotic theory, but also allows us to make a new conjecture concerning the eigenfunctions of the biharmonic operator

Surface spin flip probability of mesoscopic Ag wires

Spin relaxation in mesoscopic Ag wires in the diffusive transport regime is studied via nonlocal spin valve and Hanle effect measurements performed on permalloy/Ag lateral spin valves. The ratio between momentum and spin relaxation times is not constant at low temperatures. This can be explained with the Elliott-Yafet spin relaxation mechanism by considering the momentum surface relaxation time as being temperature dependent. We present a model to separately determine spin flip probabilities for phonon, impurity and surface scattering and find that the spin flip probability is highest for surface scattering.Comment: 5 pages, 4 figure

Evidence of Vortex Jamming in Abrikosov Vortex Flux Flow Regime

We report on dynamics of non-local Abrikosov vortex flow in mesoscopic superconducting Nb channels. Magnetic field dependence of the non-local voltage induced by the flux flow shows that vortices form ordered vortex chains. Voltage asymmetry (rectification) with respect to the direction of vortex flow is evidence that vortex jamming strongly moderates vortex dynamics in mesoscopic geometries. The findings can be applied to superconducting devices exploiting vortex dynamics and vortex manipulation, including superconducting wires with engineered pinning centers.Comment: 5 pages, 3 figure

Mother tongue language syllabi in former Serbo-Croatian speech areas

Предмет истраживања ове дисертације јесу наставни планови и програми за матерњи језик на простору некадашњег српскохрватског говорног подручја, те, према томе, рад припада домену наставне методологије. У основи његовог садржаја дато је поређење планова и програма за основне школе и гимназије четирију бивших истојезичних република: Србије, Хрватске, Босне и Херцеговине и Црне Горе. Како је њихово осамостаљивање неминовно довело и до преименовања до тада јединственог српскохрватског језика, у уводном делу дисертације осврнули смо се на језичку ситуацију од периода у коме на реформи језика дела Вук Стефановић Караџић (стварање јединственог српскохрватског језика) до распада СФРЈ, када се овај језик на поменутим територијама разједначава, добијајући нове лингвониме. Дат је осврт на структурну, генетску и социолингвистичку димензију српскохрватског језика; хронолошки су изложени: период у коме је српски језик био, можемо рећи, заједнички језик православаца, католика и муслимана (друга половина 19. века и период стварања прве Југославије), године између два светска рата, период после Другог светског рата до последњих сукоба на територији СФРЈ, те савремени догађаји.1 Поменути планови и програми за матерњи језик, који чине основни истраживачки корпус, праћени су најпре кроз дијахронијску, а потом, што чини суштински део рада, и синхронијску раван...This dissertation deals with the mother tongue language (MTL) syllabi in the former Serbo-Croatian speech area, therefore belonging to the field of teaching methodology. The main concern of the paper is the contrastive analysis of primary and secondary grammar school syllabi of the four countries that used to share one mother tongue: Serbia, Croatia, Bosnia and Herzegovina, and Montenegro. Since their secession led to the renaming of the once unified Serbo-Croatian language, the introductory part of the paper gives an overview of the language situation from the reformative work of Vuk Stefanović Karadžić (who actually created Serbo-Croatian) to the fall of SFRY when this language was differentiated into separate linguonyms. This comprises structural, genetic and sociolinguistic aspects of the language, organized in chronological order, including the period when Serbian was the common language of the Orthodox, Catholics and Muslims (second half of the 19th century as well as the constitution period of the first Yugoslavia), then the years between the two world wars, the period after the WWII till the last conflicts in former Yugoslavia, including recent events, too.2 As the basic reseach corpus, the MTL syllabi are firstly examined diachronically, and then synchronically which in fact constitutes the major part of the paper..

Variability of Phomopsis populations in sunflower (Helianthus annuus L.)

Various reports state that the sunflower disease, primarily caused by Diaporthe/Phomopsis helianthi Munt.-Cvet. et al., has a wide geographic distribution in Europe, USA, Argentina and Australia. Various Phomopsis isolates obtained during this investigation of the sunflower disease differed in conidial type (α, β, α and β). Phomopsis helianthi was the only isolate producing exclusively β-conidia and perithecia on debris (Diaporthe helianthi). The other Phomopsis isolates were saprobes on sunflower plants.nul

Position and role of security services in the modern administrative system

Положај служби безбедности у савременом управном систему, заправо, означава степен развоја демократије и организовања друштва, те говори о нивоу на коме се налази правни систем и целокупна друштвена свест. На другој страни службе безбедности, својим деловањем знатно доприносе усмеравању кретања друштва, омогућавају му несметан развој, економски и сваки други просперитет, штитећи га од унутрашњих и спољних претњи, односно доприносe квалитетнијем и сигурнијем друштву. Стављање служби безбедности у оквире цивилне контроле и јавне управе изазов је са којим су се сусреле све озбиљне државе и администрације које су, упркос свему, истрајале у овој намери. Систем организовања јавне управе у Србији и обавештајно-безбедносни апарат као његов део, према постојећим чињеницама, али и речима бројних домаћих и страних стручњака, током протеклих година, функционисао је мимо демократских принципа и ван институционалних оквира. Бројне реформе од почетка овог века до данас, свакако су допринеле изградњи организованије и модерније јавне управе, а већина њих била је усмерена у, на почетку, обуздавање, а потом, и реорганизовање и трансформацију служби безбедности ка нечему, што за сада, бар формално, личи на јавни сервис. Историјске околности, друштвено-политичко наслеђе, недемократски принципи устројства државне управе, као и недовољно развијена свест грађана о људским правима и слободама учинили су да реформе касне и да од почетка наилазе на препреке у друштву и компромисе са законодавцем, који задовољавају само форму, али никако суштину. У таквим околностима створен је систем препун нефункционалних и неадекватних законских решења у смислу контроле и прилагођавања служби безбедности оквирима савремене јавне управе, што ће у овом раду покушати да се прикаже. Као најосетљивији моменат препознат је онај који се односи на контролу рада служби безбедности и организацију и функцију контролних тела. Упоредне анализе других јавних управа и страних служби безбедности, свакако, доприносе квалитетној анализи и утврђивању степена напретка реформе јавне управе и служби безбедности у Републици Србији, као и њиховог међусобног односа. Све, до сада, постигнуто у смислу реформисања јавне управе и обевештајно-безбедносног сектора, као њеног дела у Републици Србији, свакако представља крупан искорак у правцу модерног устројства јавне управе и служби безбедности, али и демократизације друштва у целини. Међутим успостављени систем међусобне контроле и одговорности служби безбедности и јавне управе треба стално унапређивати и учинити га функционалним и стабилним, а за то је потребна снажна правна држава са свим законским механизмима и оквирима у тој области, затим непоколебљивост и одлучност власти да истраје на реформском путу ради опште користи, као и развијена друштвена свест у том смислу.The position of the security services in the present day administrative system signifies, in fact, the degree of development of democracy and the social organization, and indicates the level at which the legal system and the overall social consciousness are. On the other hand, the activities of the security services spread significant influence in directing the society, enabling it to develop uninterruptedly in economic and every other respect, protecting it from both internal and external threats, or contributing to a better and safer society. Placing the security services into the framework of civilian control and public administration is a challenge that all the developed states and administrations have faced and persisted in the intent despite the odds. According to the available data, as well as numerous domestic and foreign experts, the organization of public administration system in Serbia with the intelligence and security apparatus as its elements, has over the past years been functioning outside the democratic principles and institutional frameworks. Numerous reforms from the beginning of the century to the present day have certainly contributed to the development of a more organized and modern public administration, most of which were initially directed towards restraining and then reorganizing and transforming the security services towards something, which for the time being, at least formally, resembles a public service. The historical circumstances, socio-political heritage, non-democratic principles of the state administration system, as well as the underdeveloped awareness of citizens of human rights and freedoms have caused these reforms to arrive this late and from the outset encounter obstacles within the society and compromise with lawmakers who satisfy only the form, but not the real essence. In such circumstances, a system has been created that is full of dysfunctional and inadequate legal solutions in terms of controlling and adapting the security services to the frameworks of contemporary public administration, which this paper aims to present. The most sensitive place is the one that refers to the control of the operation of the security services and the organization and function of the control bodies. Comparative analyses of other public administrations and foreign security services contribute to the quality of the analysis and determining the level of progress of the reform of the public administration and security services in the Republic of Serbia, as well as their mutual relationship. Until now, the results achieved in terms of refining the public administration and the intelligence and security sector, as its part in the Republic of Serbia, certainly represents a major leap forward in the direction of the modern organization of the public administration and security services, as well as the democratization of the society as a whole. However, the established system of mutual control and accountability of the security services and the public administration needs to be constantly improved and made functional and stable, requiring a strong rule of law with all legal mechanisms and frameworks in that area, and also the firmness and determination of the authorities to pursue the reform path for general benefit, as well as developed social awareness in this regard. Summarizing the results achieved so far, as well as omissions, on the reform path of security services in the present day public administration of the Republic of Serbia, this paper can contribute to the analysis and review of the functionality and efficiency of the established system and organization of the intelligence and security structures of the Republic of Serbia, as well as to present the guidelines for further improvements in this area

Study of the optical power of nanophotonic soft contact lenses based on poly (2-hydroxyethyl methacrylate) and fullerene

U radu su predstavljeni rezultati komparativnih istraživanja optičke snage mekih kontaktnih sočiva (MKS) sa različitim tehnikama mjerenja koje se koriste pri finalnoj obradi kontaktnih sočiva. Tri vrste nanofotoničnih mekih kontaktnih sočiva su napravljene od standardnog polimacon materijala (Soleko SP38TM) sa inkorporiranim fulerenom C60, fulerolom C60(OH)24 i fuleren-metformin-hidroksilatom C60(OH)12(OC4N5H10)12. Za potrebe karakterizacije materijala za potencijalnu primjenu kod mekih kontaktnih sočiva, mjerena su optička svojstva mekih kontaktnih sočiva Rotleks i Nidek uređajem. Sa Rotleks uređajem dobijeni su sledeći optički rezultati: optička snaga i mapa defekata, a sa Nidek uređajem: optička snaga, snaga cilindra i ugao cilindra. Dobijene vrijednosti optičke snage i mape defekata pokazali su da optička snaga sintetisanih nanofotoničnih mekih kontaktnih sočiva je identična nominalnoj vrijednosti, dok to nije bio slučaj za standardna meka kontaktna sočiva. Takođe, kvalitet nanofotoničnih mekih kontaktnih sočiva je bolji nego kod standardnih mekih kontaktnih sočiva. Iz prikazanog se može zaključiti da je moguće sintetisati nova nanofotonična meka kontaktna sočiva željenih optičkih karakteristika, što otvara mogućnosti za njihovu primjenu u ovoj oblasti.In this paper results of comparative study of the optical power of soft contact lenses (SCL) made of standard material for SCL and nanophotonic materials with different measurement techniques used for the final contact lens controllers are presented. Three types of nanophotonic soft contact lenses were made of standard polymacon material (Soleko SP38 TM) incorporated with fullerene C 60 , fullerol C 60 (OH) 24 and fullerene metformin hydroxylate C 60 (OH) 12 (OC 4 N 5 H 10) 12. For the purposes of material characterization for potential application as soft contact lenses, the optical properties of the soft contact lenses were measured by Rotlex and Nidek device. With Rotlex device the following optical results were obtained: optical power and map of defects, while with the Nidek device: optical power, cylinder power and cylinder axis. The obtained values of optical power and map of defects showed that the optical power of synthesized nanophotonic soft contact lens is same to the nominal value, while this was not the case for the standard soft contact lens. Also, the quality of the nanophotonic soft contact lens is better than the standard one. Hence, it is possible to synthesize new nanophotonic soft contact lenses of desired optical characteristics, implying possibilities for their application in this field

Kinetics and mechanism of synthetic CoS oxidation process

The results of investigation of kinetics and mechanism for synthetic a-CoS oxidation process are presented in this paper. Based on experimental data obtained using DTA and XRD analysis and constructed PSD diagrams for Co-S-O system, mechanism of synthetic a-CoS oxidation process is suggested. Characteristic kinetic parameters were obtained for experimental isothermal investigations of desulfurization degree using Sharp method

EXAMPLES OF LCA METHODOLOGY IMPLEMENTATION IN STEEL INDUSTRY

Steel industry kept pace with actual trends for environmental protection in many ways – through different technological improvements considering environment protection, important share of recycling in the steel production, design of so called “eco-steels”, materials designed according to recent environmental directives and legislatives, etc. In the frame of steel production monitoring, LCA methodology is very important for obtaining an accurate environmental picture of a process, due to the fact that the process should be evaluated over its entire life cycle. A number of tools and methodologies have been developed in recent years to assess the potential environmental impacts associated with a product, process or activity during its entire life cycle. The examples of Life Cycle Assessment (LCA) are used by large steel industrial companies as potentially helpful tool for improving the production processes, efficiency of resource utilization and significantly reduction of waste generation and emissions are presented in this paper

The clay minerals from greda deposit

The term "clay" refers to natural materials composed of fine minerals, which in their composition contain water molecules, which give it the property of plasticity, which is lost by drying processes. The basic physical and chemical characteristics of clay are low permeability, the possibility of cation exchange, thermal structural stability, swelling processes. These characteristic properties appear as a consequence of the crystal structure, in which the layers of SiO4, tetrahedra, extend infinitely in two dimensions. In this paper are presented the basic structural and crystallochemical properties of clay from Greda deposit