The crack kinking out of an interface

Kinking of a plane strain crack out of an interface between the two dissimilar isotropic elastic materials is analyzed. Analysis is focused on the initiation of kinking and thus the segment of the crack leaving the interface is imagined to be short compared to the segment in the interface. The analysis provides the stress intensity factors and energy release rate of the kinked cracks in terms of the corresponding quantities for the interfacial crack. The energy release rate is enhanced if the crack heads into the more compliant material and is diminished if the crack kinks into the stiff material

Generisanje superkontinuuma i primena u optičkim telekomunikacijama

Supercontinuum generation is a phenomenon ofsignal spectrum broadening, due to the interplay between nonlinear and dispersive effects of the nonlinear medium. This phenomenon has been the subject of numerous studies in different mediums, due to its wide range of applications in a number of fields, such as tomography, metrology, spectroscopy, biomedical optics and in the field of optical telecommunications. For the analysis and modeling of the supercontinuum characteristics, it is crucial to select a medium in which signal propagation and supercontinuum generation are performed. For the application of supercontinuum in the field of optical telecommunications, optical fibers of the specific microstructure, i.e.PCF (Photonic Crystal Fiber) fibers are used, due to the high nonlinearity and the ability to model its dispersion profile, by modeling the structure of the fiber itself. In addition to the dispersive and nonlinear characteristics of the fiber, characteristics of the supercontinuum spectrum depend on a number of input signal parameters, such as wavelength, power, shape and duration of the input pulse. These parameters significantly influence the dynamics of the supercontinuum, in terms of the formation of processes responsible for the generation of supercontinuum, such as soliton fission, dispersive waves generation, self-phase modulation, etc. On the other hand, they also affect the width of the supercontinuum output spectrum and its coherence, which is crucial for supercontinuum applications in different fields. This doctoral thesis presents the investigation of supercontinuum characteristics in PCF fibers of different dispersion profiles, for different input signal parameters. Supercontinuum generation is performed at wavelengths corresponding to the first, second and third optical windows. The processes responsible for spectrum spread in different optical windows and dispersion regimes, for different values of the input parameters, are analyzed. Supercontinuum generation in PCF fibers is numerically investigated and the process itself was modeled by the nonlinear Schrödinger equation. Also, the thesis gives an overview of the probability of distribution of extreme events, RW (Rogue Wave) waves, in supercontinuum generated in the anomalous dispersion regime. Furthermore, study was focused on determining the characteristics of the supercontinuumspectrum and its coherence in the anomalous and normal dispersive regime, in order to define the optimaldispersion regime, the type of PCF fiber and the input parameters of the signal, to obtain supercontinuum spectrum, suitable for use as a multi-wavelength optical source in WDM (Wavelength Division Multiplexing) systems

PRODUCTION OF HETEROGENEOUS SUPERALKALI CLUSTERS Li n F (n= 2 -6) BY KNUDSEN -CELL MASS SPECTROMETRY

The superalkali clusters are important because they can be considered as potential building block for the assembly of novel nanostructured materials with unique structural, electronic, optical, magnetic, and thermodynamic properties. We have modified and used the Knudsen cell mass spectrometer in order to obtain and measurement of the ionization potentials of the superalkali clusters. In this work the clusters Li n F (n = 2 -6) have produces in the vapor over a mixture of lithium fluoride and lithium iodide by means of Knudsen cell which is placed into ionization chamber of the magnetic sector mass spectrometer. The simultaneous production and mass spectrometric detection of the ionic of clusters provide information on the conditions of formation and the distribution of these ion species. It is observed that the ions of clusters with an even numbered of lithium atoms are more stable than the ions of clusters with an odd numbered of lithium atoms. The clusters Li 5 F and Li 6 F were detected experimentally for the first time with their ionization energies of (4.29±0.25) eV, and (4.24±0.25) eV, respectively

Solid state synthesis of extra phase-pure Li4Ti5O12 spinel

Extra phase-pure Li4Ti5O12 spinel with particle sizes less than 500 nm was synthesized by solid state reaction of mechanochemicaly activated mixture of nano anatase and Li2CO3 for a very short annealing time, 4 h at 800°C. Structural and microstructural properties, the mechanism of solid state reaction between anatase and Li2CO3 as well as thermal stability of prepared spinel were investigated using XRPD, SEM and TG/DSC analysis. The mechanism of reaction implies decomposition of Li2CO3 below 250ºC, formation of monoclinic Li2TiO3 as intermediate product between 400 and 600°C and its transformation to Li4Ti5O12 between 600-800ºC. The spinel structure is stable up to 1000ºC when it is decomposed due to Li2O evaporation

Supplementary data for the article: Veljković, D. Ž.; Medaković, V. B.; Andrić, J. M.; Zarić, S. D. C-H/O Interactions of Nucleic Bases with a Water Molecule: A Crystallographic and Quantum Chemical Study. CrystEngComm 2014, 16 (43), 10089–10096. https://doi.org/10.1039/c4ce00595c

Supplementary material for: [https://doi.org/10.1039/c4ce00595c]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1868

Tims and maldi tof of endohedral metallofullerenes

Mass spectral studies (both TIMS – thermal ionization and MALDI TOF – matrix-assisted laser desorption time-of-flight mass spectrometry) of the endohedral metallofullerenes, Li@C60,Li2C70 and 99mTc@C70,provided detailed structural and reactivity information about these unusual species. MS experiment revealed that both fullerenes and endohedral metallofullerenes fragment by multiple C2 loss. However, a difference in the terminal fragmentation products was observed for metallofullerene relative to C60, suggesting that the encapsulation metal strongly impactsthe fragmentation product. Singly charged cations of the metallofullerenes (M@Cn + ) were completely unreactive in the gas phase with oxygenated compounds such as ethylene oxide: however, the corresponding neutral species appear to react readily with oxygenated species. Collisional dissociation of the ionized endohedral fullerenes listed above revealed multiple C2 loss (either as sequential C2 loss or larger C2n eliminations) to generate similar terminal fragmentation products, which might be predicted due to the similar ionic radii of the encapsulated metals. The observed ionization energies of endohedral molecules were 5.9 ± 0.1 eV, 5.3 ± 0.1 eV and 5.7 ± 0.1 eV, respectively.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200

Surface ionization study of the non- stoichiometric LnFn-1 (n = 4 – 6) clusters

In this study we are presenting the results of the surface ionization of LinFn-1 (n=4- 6) clusters on rhenium surface impregnated with fullerenes using the magnetic mass spectrometer. The Li5F4 nanocubic cluster was detected for the first time. We determined values of ionization energies for Li4F3 and Li6F5, they are 4,3±0,2 eV, 4,0±0,2eV, respectively. The ionization energies agreed with theoretical ionization energies obtained by ab initio method, which indicates the excess electron localized in a specific site for non-stoichiometric clusters. The first ionization energy value for the Li4F3 was in accordance with earlier results obtained experimentally using photoionization time-of-flight mass spectrometer. There are currently no reliable experimental data for the ionization energy of Li6F5 cluster.Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

The comparison of gamma-radiation and electrical stress influences on oxide and interface defects in power VDMOSFET

The behaviour of oxide and interface defects in n-channel power vertical double-diffused metal-oxide-semiconductor field-effect transistors, firstly degraded by the gamma-irradiation and electric field and subsequently recovered and annealed, is presented. By analyzing the transfer characteristic shifts, the changes of threshold voltage and underlying changes of gate oxide and interface trap densities during the stress (recovery, annealing) of investigated devices, it is shown that these two types of stress influence differently on the gate oxide and the SiO2-Si interface. [Projekat Ministarstva nauke Republike Srbije, br. OI171026

Methods of surface ionization for the measurement of chlorine’s isotopic composition

Jedinjenja hlorata i perhlorata koja se koriste kao herbicidi, pogonska čvrsta goriva i eksplozivi, i sve češće se prepoznaju kao zagađivači podzemnih voda [1]. Perhlorati su posebno opasni jer ometaju proizvodnju hormona u štitnoj žlezdi. Hlor je podložan izotopskom frakcionisanju fizičkim i hemijskim procesima. Varijacije u atomskim masama, kao i u zastupljenosti izotopa hlora su posledica njegovog izotopskog frakcionisanja tokom fizičkih, hemijskih i bioloških procesa. Upravo, te varijacije su korisne za određivanje porekla supstance i proučavanje ekoloških, hidroloških i geoloških procesa. Takođe, analizom izotopa hlora može se utvrditi i priroda zagađivača životne sredine odnosno da li je njegovo poreklo antropogeno ili ne. Informacije mogu biti važne iz pravnih razloga i za remedijaciju kontaminiranog područja [2, 3]. Hlor se u prirodi javlja u obliku dva stabilna izotopa 35Cl i 37Cl (relativnih atomskih masa, respektivno 34,968 8527 i 36,965 9026), čiji relativni izotopski sastav je 0,7553 i 0,2547 [4]. Merenje odnosa stabilnih izotopa hlora (n(37Cl)/n(35Cl)), kao i molske frakcije 36Cl (n(36Cl)/n(Cl)) pruža korisne informacije o poreklu hlorata i perhlorata u okruženju [2, 3]. Ranija merenja promene odnosa stabilnih izotopa hlora rađena su pomoću magnetnog masenog spektrometra sa površinskom jonizacijom u negativnom modu direktnim praćenjem jona Cl- [5], ili određivanjem promena izotopskog sastava praćenjem jona jedinjenja CH3 Cl+ [6]. Danas se metodom površinske jonizacije radi ispitivanja izotopskog sastava ne prate direktno joni hlora, već jedinjenja kao što su „superalkalni” klasteri tipa M2 Cl+ (M-alkalni metali). Razlog je, vrlo niska energija jonizacije pomenutih klastera (u nekim slučajevima niža od energije jonizacije cezijuma) što omogućava njihovu vrlo jednostavnu detekciju u masenom spektru [7]. Iako je ova metoda precizna i pouzdana, vrlo je skupa. Broj analiza izotopa hlora pomoću ugljovodonika koji u sastavu imaju hlor kao što je trihloretilen je u porastu, jer su ove vrste važni zagađivači životne sredine. Analiza kontinuiranog protoka trihloretilena molekula, bilo gasnom hromatografijom/izotopskom masenom spektrometrijom (GC/IRMS) ili sa masenom spektrometrijom GC/kvadrupol (GC/qMS), je inovativno analitičko rešenje, ali uprkos ranijim implementacijama, nedostaje joj rutinska aplikacija [8]. Pored navedenih tehnika u površinske metode jonizacije spada i masenospektrometrijska metoda laserske desorpcije i jonizacije (LDI). Preliminarni rezultati ukazuju da se „superalkalni“ klasteri tipa M2 Cl+ mogu detektovati navedenom metodom. S obzirom na jednostavnost korišćenja i njenu ekonomsku isplatljivost, analiza i ispitivanje promene izotopskog sastava pomoću LDI metode može predstavljati važan korak u analitic

Numerical study of the supercontinuum generation in the telecommunications windows in photonic crystal fiber

This research explores a supercontinuum (SC) generation in silica based highly nonlinear photonic crystal fiber of near infrared window, suitable for application in the field of telecommunications [1]. Results obtained here could be of interest in attempts to improve the characteristics of multi-wavelength sources for dense wavelength division multiplexing (DWDM) systems. We study numerically SC dynamics in both spectral and temporal domain in three different optical windows, at referent wavelengths of 835nm, 1300nm and 1550 nm. The dependence of SC properties on the input pulse power, shape and the value of the chirp is investigated in details. It has been shown that the most intense spread of SC spectrum at fiber output is obtained in the third optical window, while the input signal shape, power and duration stayed unchanged [2]. The shape of the initial pulse was the most influential in the second optical window, where the simulated SC has flat and smooth profile, covering the wavelength range from 1000 nm to 2000 nm. In addition, we examine the SC spectrum coherence in all of the three optical windows with respect to different input pulses. On the other hand, the richest SC dynamics is observed in the first window, where the appearance of high intensity events of the rogue wave type is reported [3].VII International School and Conference on Photonics : PHOTONICA2019 : Abstracts of Tutorial, Keynote, Invited Lectures, Progress Reports and Contributed Papers; August 26-30; Belgrad