Search results for "Optica"
showing 10 items of 7696 documents
A Mission Impossible? Learning the Logic of Space with Impossible Figures in Experience-Based Mathematics Education
2016
Most visual effects based on mathematically and physically describable phenomena and formalizable processes. Creating visual illusions, paradox structures and ‘impossible’ figures through playful and artistic procedures, holds an exciting pedagogical opportunity for raising students’ interest towards mathematics and natural sciences and technical aspects of visual arts. The Experience Workshop Math-Art Movement has a number of pedagogical methods, which are connected to visual paradoxes and perspective illusions. In the first part of our article, we introduce classroom exercises connected to the Hungarian artist Tamás F. Farkas’s paradox structures and impossible figures. There are certain …
Harnessing Fluorescence versus Phosphorescence Branching Ratio in (Phenyl)n-Bridged (n = 0–5) Bimetallic Au(I) Complexes
2013
We have designed and synthesized a series of Au(I) complexes bearing either an alkynyl–(phenylene)n–diphosphine (A-0–A-3) or a (phenylene)n–diphosphine (B-1–B-5) bridge, among which the effective distance between Au(I) and the center of the emitting ππ* chromophore can be fine-tuned via the insertion of various numbers of phenylene spacers. We then demonstrated for the first time in a systematic manner the decrease of rate constant for S1 → T1 intersystem crossing (ISC) kisc as the increase of the effective distance. The results also unambiguously showed that the phosphorescence could be harvested via higher S0 → Sn (n > 1) electronic excitation, followed by fast Sn → Tm ISC and then the po…
Origin of the large spectral shift in electroluminescence in a blue light emitting cationic iridium(III) complex
2007
A new, but archetypal compound [ Ir( ppy- F-2) (2)Me(4)phen] PF6, where ppy- F2 is 2-(2',4'- fluorophenyl) pyridine and Me(4)phen is 3,4,7,8- tetramethyl- 1,10- phenanthroline, was synthesized and used to prepare a solid-state light-emitting electrochemical cell (LEEC). This complex emits blue light with a maximum at 476 nm when photoexcited in a thin film, with a photoluminescence quantum yield of 52%. It yields an efficient single-component solid-state electroluminescence device with a current efficiency reaching 5.5 cd A(-1) and a maximum power efficiency of 5.8 Lm Watt(-1). However, the electroluminescence spectrum is shifted with respect to the photoluminescence spectrum by 80 nm resul…
A study of physical processes in microplasma capillary discharges
2011
We continue the research of low-pressure capillary discharge lamps of 500 μ m in radius in Ar/Hg, Kr/Hg and Xe/Hg mixtures. In the previous paper, an experimental approach which combines the optical emission spectroscopy (OES) and tomographic methods was developed to study the capillary discharge. The present work is focused on interpretation of the tomographic reconstruction results for understanding the physical processes occurring in a capillary plasma. Analyzing the results of reconstruction, it was concluded that the radial profiles of Ar, Kr and Xe emission coefficients are in a good agreement with the Schottky theory. According to the Schottky model, ionization processes in plasma a…
Electronic and magnetic structure ofLa0.875Sr0.125MnO3calculated by means of hybrid density-functional theory
2007
We present the results of ab initio calculations on magnetic and electronic structures of La1�xSrxMnO3 at low doping, x =1/8. Using the B3LYP hybrid exchange-correlation functional within the framework of densityfunctional theory, we predict a ferromagnetic ground state for La0.875Sr0.125MnO3 in both the low-temperature orthorhombic and the high-temperature pseudocubic phases. This is in contrast to its parent compound LaMnO3, for which we find in agreement with experiment the layered antiferromagnetic state to be the most stable one. The calculated density of states and bond population analysis suggest a tendency of formation of half-metallic spin states in the band gap of both structures.
Microstructural and magnetic characterization of dusts from a stone crushing industry in Birbhum, India
2010
Abstract Stone dust sample collected from a stone crushing industry situated at Muhammad Bazar in Birbhum, India, is studied for its physical characterization using various techniques. Morphology and compositional analysis of the stone dust by scanning electron microscopy (SEM) reveal that the dust is an agglomeration of many tiny particles (0.32–2.12 μm), mostly having sharp edges, as well show microstructure heterogeneity. Elements present in the sample are detected by energy dispersive X-ray spectrometry (EDX). The X-ray diffraction (XRD) pattern analysis shows that the sample mainly contains minerals like anorthite, augite, esseneite and albite. An overall antiferromagnetic interaction …
Ab initio calculations of Nb doped SrTiO3
2010
We present and discuss the results of the large scale Hartree–Fock calculations of Nb impurities substituting for Ti ions in SrTiO3 using ab initio computer code CRYSTAL and several supercells containing up to 135 atoms. The local structure optimisation, the electronic charge redistribution, chemical bond covalence and the band-structure changes induced by the defect are analysed. According to the results of our calculations, Nb is a shallow donor; six nearest O ions are slightly displaced outwards from the Nb ion. The calculated bond population between nearest Ti and O ions (64 me) is much larger than that between Nb and O ions (8 me), since Nb impurity is more ionic than the host Ti.
Time evolution of non-lethal infectious diseases: a semi-continuous approach.
2005
A model describing the dynamics related to the spreading of non-lethal infectious diseases in a fixed-size population is proposed. The model consists of a non-linear delay-differential equation describing the time evolution of the increment in the number of infectious individuals and depends upon a limited number of parameters. Predictions are in good qualitative agreement with data on influenza.
Photodynamics of a Molecular Water-Soluble Nanocluster Identified as Au130(pMBA)50
2015
Photodynamics of a highly monodisperse sample of a water-soluble gold nanocluster tentatively identified as Au130(pMBA)50 (pMBA = p-mercaptobenzoic acid) was studied by mid-IR transient absorption spectroscopy with visible excitation. The observed long-lived excited states (>1 ns) indicate a molecular behavior of the cluster. By combining the transient absorption data with DFT calculation results the observed relaxation dynamics could be fully explained by identifying several relaxation processes involving singlet and triplet manifolds. The results indicate that the cluster may have interesting transient magnetic properties due to a long-lived triplet population.
SU-8 viļņvadu izveide ar tiešā ieraksta lāzera litogrāfijas tehniku un to optisko īpašību raksturošana
2016
Kopš 20.gs. beigām lieli pūliņi ieguldīti telekomunikāciju attīstībā, arvien tiek meklēti jauni materiāli, lai aizvietotu elektroniskās komponentes integrētajās shēmās, jo tās ir ierobežojošais faktors informācijas pārvades ātrumam. Viens no risinājumiem būtu veidot shēmas, kas satur tikai optiskās komponentes. Optisko komponenšu pamatā ir viļņvadi, kuriem jābūt ar noteiktām optiskām īpašībām. Viena no perspektīvākajām materiālu klasēm pielietojumiem fotoniskās integrālās shēmās ir organiskie materiāli. Darbā aprakstīta tīru un funkcionalizētu organisku SU 8 viļņvadu izgatavošana ar tiešā ieraksta lāzera litogrāfijas tehniku. Ir aprakstīti viļņvadu izgatavošanas soļi un metodes ierobežojumi…