Induction motor IFOC based speed-controlled drive with asymptotic disturbance compensation

This paper presents the design of digitally controlled speed electrical drive, with the asymptotic compensation of external disturbances, implemented by using the IFOC (Indirect Field Oriented Control) torque controlled induction motor. The asymptotic disturbance compensation is achieved by using the DOB (Disturbance Observer) with the IMP (Internal Model Principle). When compared to the existing IMP-based DOB solutions, in this paper the robust stability and disturbance compensation are improved by implementing the minimal order DOB filter. Also, the IMP-based DOB design is improved by employing the asymptotic compensation of all elemental or more complex external disturbances. The dynamic model of the IFOC torque electrical drive is, also, included in the speed-controller and DOB section design. The simulation and experimental measurements presented in the paper illustrate the effectiveness and robustness of the proposed control scheme

Stress engineering at the nanometer scale: Two-component adlayer stripes

Spontaneously formed equilibrium nanopatterns with long-range order are widely observed in a variety of systems, but their pronounced temperature dependence remains an impediment to maintain such patterns away from the temperature of formation. Here, we report on a highly ordered stress-induced stripe pattern in a two-component, Pd-O, adsorbate monolayer on W(110), produced at high temperature and identically preserved at lower temperatures. The pattern shows a tunable period (down to 16 nm) and orientation, as predicted by a continuum model theory along with the surface stress and its anisotropy found in our DFT calculations. The control over thermal fluctuations in the stripe formation process is based on the breaking/restoring of ergodicity in a high-density lattice gas with long-range interactions upon turning off/on particle exchange with a heat bath.Comment: 6 pages, 4 figure

Mn L2,3_{2,3} edge resonant x-ray scattering in manganites: Influence of the magnetic state

We present an analysis of the dependence of the resonant orbital order and magnetic scattering spectra on the spin configuration. We consider an arbitrary spin direction with respect to the local crystal field axis, thus lowering significantly the local symmetry. To evaluate the atomic scattering in this case, we generalized the Hannon-Trammel formula and implemented it inside the framework of atomic multiplet calculations in a crystal field. For an illustration, we calculate the magnetic and orbital scattering in the CE phase of \lsmo in the cases when the spins are aligned with the crystal lattice vector ${\vec a}$ (or equivalently ${\vec b}$) and when they are rotated in the $ab$-plane by 45$^{\circ}$ with respect to this axis. Magnetic spectra differ for the two cases. For the orbital scattering, we show that for the former configuration there is a non negligible $\sigma \to \sigma'$ ($\pi \to \pi'$) scattering component, which vanishes in the 45$^\circ$ case, while the $\sigma \to \pi'$ ($\pi \to \sigma'$) components are similar in the two cases. From the consideration of two 90$^\circ$ spin canted structures, we conclude there is a significant dependence of the orbital scattering spectra on the spin arrangement. Recent experiments detected a sudden decrease of the orbital scattering intensity upon increasing the temperature above the N\' eel temperature in \lsmo. We discuss this behavior considering the effect of different types of misorientations of the spins on the orbital scattering spectrum.Comment: 8 figures. In the revised version, we added a note, a reference, and a few minor changes in Figure 1 and the text. Accepted in Physical Review

Supplementary data for article: Sostaric, A.; Stojic, S. S.; Vukovic, G.; Mijic, Z.; Stojić, A.; Gržetić, I. Rainwater Capacities for BTEX Scavenging from Ambient Air. Atmospheric Environment 2017, 168, 46–54. https://doi.org/10.1016/j.atmosenv.2017.08.045

Supplementary material for: [ https://doi.org/10.1016/j.atmosenv.2017.08.045]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2539]Related to accepted version:[http://cherry.chem.bg.ac.rs/handle/123456789/3007

Temperature dependence of surface stress across an order-disorder transition: p(1x2)O/W(110)

Strain relaxations of a p(1x2) ordered oxygen layer on W(110) are measured as a function of temperature across the disordering transition using low-energy electron diffraction. The measured strains approach values of 0.027 in the [1-10] and -0.053 in the [001] direction. On the basis of the measured strain relaxations, we give quantitative information on temperature-dependent surface stress using the results of ab initio calculations. From the surface formation energy for different strains, determined by first-principles calculations, we estimate that surface stress changes from -1.1 for the ordered phase to -0.2N/m for the disordered one along [1-10], and from 5.1 to 3.4 N/m along [001]. Moreover, our observation that the strains scale inversely with domain size confirms that the strain relaxation takes place at the domain boundaries.Comment: 8 pages, 5 figure

Transformers as a potential for soil contamination

The aim of this paper is to investigate the presence of PCBs and heavy metals in the surrounding soil and also in the soil of the receiving pit located below the PCB contaminated transformer. Concentrations of PCBs in our samples are ranged from 0,308 to 0,872 mg/kg of absolutely dry soil

Spatio-temporal distribution of aerosols and volatile organic compounds in troposphere: libar and mass spectrometry

U disertaciji je prikazano istraživanje sprovedeno u cilju određivanja porekla, prostorne raspodele i dinamike isparljivih organskih jedinjenja i aerosola u urbanoj sredini Beograda. Baza podataka korišćena za analizu aerosola obuhvata višegodišnje masene koncentracije suspendovanih čestica PM10, podatke o njihovom hemijskom sastavu (sadržaj čađi, As, Cd, Cr, Mn, Ni, Pb, Cl-, Na+, K+, Mg, Ca, NO3 -, SO4 2-, NH4 + i benzo(a)pirena), meteorološke parametre i visinu planetarnog graničnog sloja. Podatke korišćene za analizu isparljivih organskih jedinjenja čine koncentracije 36 molekulskih masa izmerene masenim spektrometrom sa transferom protona (PTR-MS), koncentracije neorganskih gasnih oksida (NOx, NO2, NO, SO2 i CO), visina planetarnog graničnog sloja dobijena na osnovu Lidar merenja i meteorološki parametri. Detaljna analiza zagađujućih materija izvršena je primenom brojnih metoda, kao što su: polarna klaster analiza i CBPF za određivanje položaja i uticaja izvora u blizini mernog mesta; receptorski modeli PMF i Unmix za identifikaciju izvora i određivanje njihovog doprinosa izmerenim koncentracijama; TSA, TCA, PSCF i CWT modeli za utvrđivanje doprinosa transporta zagađujućih materija i geografskih oblasti iz kojih potiču; multivarijativne metode za prognozu emisije; i HYSPLIT model za određivanje disperzije prognoziranih epizoda velikog zagađenja. U disertaciji je predložen i nov pristup analizi transporta zagađujućih materija koji podrazumeva specifičnu selekciju i klasterizaciju reprezentativnih trajektorija i uklanjanje doprinosa lokalnih izvora. Rezultati istraživanja pokazuju da su koncentracije suspendovanih čestica u urbanoj sredini Beograda značajno više u odnosu na druge evropske gradove. Njihove varijacije tokom prethodnih dvanaest godina nastaju kao posledica različitih faktora, među kojima su najznačajniji prelazak na daljinski sistem grejanja i remont termoelektrana u okruženju, varijacije intenziteta saobraćaja, ali i promene meteoroloških uslova. Rezultati polarne klaster, CBPF i TSA analize pokazuju da su dominantni izvori suspendovanih čestica lokalnog karaktera. Doprinosi regionalnih izvora emisije menjali su se u zavisnosti od meteoroloških uslova i sezona, ali nisu prelazili 19% godišnjih srednjih vrednosti koncentracija. Primenom receptorskog modela Unmix identifikovana su četiri izvora suspendovanih čestica: sagorevanje fosilnih goriva i biomase koji u ukupnim...This dissertation presents the research conducted for the purpose of determining the origin, spatial distribution and dynamics of volatile organic compounds (VOC) and aerosols in an urban area of Belgrade. The dataset used for the aerosol analysis include a multi-year database of PM10 mass concentrations, data on the chemical composition of the suspended particles (black carbon content, As, Cd, Cr, Mn, Ni, Pb, Cl-, Na+, K+, Mg, Ca, NO3 -, SO4 2-, NH4 + and benzo(a)pyrene), meteorological parameters and planetary boundary layer height (PBL). The database used for the VOC analysis includes concentrations of 36 molecular masses measured by means of protontransfer- reaction mass spectrometry (PTR-MS), concentrations of inorganic gaseous pollutants (NOx, NO2, NO, SO2 and CO), PBL height obtained by means of Lidar measurements and meteorological parameters. A detailed analysis of pollutants was performed by means of various methods such as: cluster analysis and CBPF for determining the location and influence of sources in the vicinity of the measurement site; PMF and Unmix receptor models for source apportionment and estimation of their contributions to measured concentrations; TSA, TCA, PSCF and CWT models for the assessment of the share of pollutant transport, as well as their geographical area of origin; multivariate methods for the purpose of emission forecast; and HYSPLIT model to determine the dispersion of forecasted high pollution episodes. Furthermore, the thesis proposes a new approach to the analysis of pollution transport, which implies the specific selection and clustering of representative trajectories and removal of local source contributions. Research results indicate that the concentrations of total suspended particles in an urban area of Belgrade are significantly higher than in other European cities. Over the past 12 years, their variations have been driven by numerous factors, predominantly by the transition to district heating system and overhaul of the neighbouring thermal power plants, variations in traffic intensity and changes in meteorological conditions. The results of bivariate cluster, CBPF and TSA analysis show that the dominant sources of PM10 are distributed in the vicinity of the measurement site. The contributions of potential regional emission sources varied depending on the meteorological..

Influence of electromagnetic and nuclear radiation in medicine for therapy and diagnosis through processes, facts and statistical analysis

Contemporary medicine (biomedicine) cannot be imagined without diagnostics and therapeutic methods based on nuclear, laser, acoustical and other processes. The application of these methods is linked to common computer support, signal processing, measuring monitoring techniques, high degree of automatization, and image analyses. The paper analysed contemporary technical issues related to neonatology, ophthalmology, based on the influence of nuclear radiation and laser beams. Some statistical processing and presentations of results obtained in the IGA KCS Hospital, Belgrade, Serbia, in curing vision of prenatal type new-borns with a different degree of pathological state of retinopathy of prematurity are presented. The general conclusion is that, in spite of the good results, a multidisciplinary approach is needed for a deeper understanding of the role of lasers and laser techniques in medicine as well as possible couplings. Potential new applications of lasers important for the fields of neonatology and ophthalmology were also considered

Strain relaxation in small adsorbate islands: O on W(110)

The stress-induced lattice changes in a p(1x2) ordered oxygen layer on W(110) are measured by low-energy electron diffraction. We have observed that small oxygen islands show a mismatch with the underlying lattice. Our results indicate that along [1-10] the average mismatch scales inversely with the island size as 1/L for all oxygen coverages up to 0.5 ML, while along [001] it is significant only for the smallest oxygen islands and scales as a higher power of the inverse island size. The behaviour along [1-10] is described by a one-dimensional finite-size Frenkel-Kontorova model. Using this model, together with calculated force constants, we make a quantitative estimate for the change of surface-stress upon oxygen adsorption. The result is consistent with our ab-initio calculations, which give a relative compressive stress of -4.72 N/m along [1-10] and a minute relative tensile stress of 0.15 N/m along [001]. The scaling along [001] is qualitatively explained as an effect induced by the lattice relaxation in the [1-10] direction.Comment: 22 pages, 5 figure