Data-Driven Methods for Distribution Modeling and Sensing

The electric power industry has set critical renewable energy targets to promote low-emission growth in power supply. However, the integration of variable and uncertain renewable energy sources into the power grid adds complexity to its operations. This complexity is further amplified by the emergence of &ldquo;grid-edge&rdquo; technologies such as home battery storage, electric vehicles, and behind-the-meter renewables like rooftop solar. Collectively referred to as distributed energy resources (DERs), these clean energy technologies emphasize the importance of modernizing grid operations to ensure reliability and quality of power supply, particularly at the grid edge. But with inadequate tools to cope with limited distribution grid visibility, modernizing its operating practices is a challenge. This calls for the development of specialized tools that can operate effectively despite the lack of reliable network models and abundant measured data. This dissertation focuses on the design and study of data-driven algorithms that enable the realization of such tools, thereby contributing to data-driven methods for distribution modeling and sensing. The dissertation is divided into two distinct parts, each targeting a specific challenge related to distribution voltage determination. The first part (Chapter 2 through Chapter 4) considers data-driven approaches for enhancing present and look-ahead situational awareness of distribution gridvoltages to effectively manage the increasing presence of DERs. Previous efforts to improve visibility into distribution system states frequently assume that the system model is fully known. In reality, however, electric distribution utilities usually lack confidence in the accuracy of these models, which limits the practicality of such solutions. In response to this, Part I of the thesis explores alternative methods that do not require knowledge of the network model. Two promising data-driven methods have been identified: machine learning (ML) and matrix completion techniques. The thesis studies both methods, focusing on their applications to model-free voltage estimation under low observability conditions (Chapter 2 and Chapter 3) and model-free voltage prediction with uncertainty estimates (Chapter 4). The second part of the thesis (Chapter 5) shifts its focus from model-free approaches to power flow modeling for high-fidelity calculation of voltage profiles in radial distribution configurations. Motivation lies in increasing the accuracy of voltage solutions over a wider range of operating points while preserving the mathematical simplicity of the linear power flow model. To accomplish this, Part II of the thesis introduces a distribution power flow linearization that combines elements of both the underlying network model and the ML methodology. Gaussian process (GP) regression is chosen as the methodology for its capacity to generate closed-form predictions with quantified uncertainties while requiring minimal data (as also explored in Chapter 4). Within this framework, a new model is proposed and evaluated, which uses a GP-based parameterization to establish a linear relationship between squared voltages and net-load (load minus renewable generation) power injections. This new model is therefore coined as a parameterized linear power flow model.</p

Sukcesije biljnih zajednica na požarištima planine Vidlič

Cilj ovog rada je praćenje sukcesije na požarištima krečnjačkog terena planine Vidlič u jugoistočnoj Srbiji nakon požara 2007. godine koji je zahvatio ogromnu površinu planine. Na osnovu višegodišnjeg terenskog istraživanja oformljena je obimna herbarska zbirka kao i velika količina florističkih, fitocenoloških i ekoloških informacija uobličenih u vidu baze podataka, koji govore o flori i vegetaciji na pomenutom području. Sistematskim terenskim istraživanjem utvrđeno je da floru planine Vidlič izgrađuje 1265 taksona u rangu vrste i podvrste. Sakupljeno je 10985 herbarskih uzoraka sa terena planinskog venca Via, što predstavlja zbir prikupljenih herbarskih i literaturnih podataka. Radi lakše analize zabeleženih podataka, koji se odnose na opožarene i neopožarene površine,uvedene su tri skraćenice: Po, NP i CP. Skraćenicom Po (“požarište”) označene su sve opožarene površine, uključujući požarišta u zoni bukovih šuma, požarišta u zoni hrastovih šuma I požarište otvorenih staništa odnosno suvih pašnjaka i kamenjara. Skraćenicom NP (“neopožarene površine”), označene su sve neopožarene površine, koje se nalaze u neposrednoj okolini požarišta odnosno svih opožarenih površina. Skraćenicom C

Allergenic potency of kiwi fruit during fruit development

Food allergies, including kiwi fruit allergy, have been the subject of extensive research in the last few years. The aim of this study was to examine a possible relationship between the developmental stage of kiwi fruit and its allergenic potency. The protein and allergen patterns of kiwi fruit extracts in September, October, November and December fruit in the period from 2000-2002 were analysed. One of the factors that may contribute to the difficulties in proposing well-defined and standardized fruit extracts should also be the time of fruit harvesting. In this particular case, when the kiwi fruit was edible throughout November and December, we showed discrepancies in allergen content and potencies both in qualitative and quantitative terms. Two major allergens of kiwi fruit, Act c 1 and Act c 2, mainly accounted for the highest allergenic potential of November kiwi extract in vivo and in vitro. Not only the content of major allergens, but also the ratio of different proteins and even isoforms of the same allergen (Act c 2) change with fruit ripening. These findings should be taken into account during preparation of extracts for allergy diagnosis

Effects of different mechanical treatments on structural changes of lignocellulosic waste biomass and subsequent Cu(II) removal kinetics

In this paper, the character of structural changes induced by different mechanical treatments to Prunus persica stones (PSs), and its subsequent effect on biosorption kinetics of Cu(II) were investigated. PSs were processed in vibratory disk mill (PS-V) and ultra-centrifugal mill (PS-C) and characterized by XRD, BET, SEM and FTIR spectroscopy. It was shown that PS-V was smaller and more reactive with less crystallinity index and hydrogen bond intensity compared to PS-C. In opposite, surface area of the PS-C was bigger than that of the PS-V. The total pore volume was about threefold, while the volume of micro pores was 9.29 times higher in PS-Cs than in PS-Vs. The kinetics of Cu(II) biosorption by both PSs was tested through various kinetic models: pseudo-first and pseudo-second order rate equations, Elovich equation, Boyd model, Weber–Morris and Urano–Tachikawa intraparticle diffusion model. For both sample types, Cu(II) biosorption occurred through combination of intraparticle and film diffusion mechanism, while kinetic results were best described by the pseudo-second order kinetic model. At the same time, the results indicated that together with kinetic rate the biosorption capacity of PS-C (21.20 mg g−1) was higher than that of PS-V (16.30 mg g−1). Mechanical activation like crushing and grinding will change material particle size, specific surface area and porosity, as well as its crystallinity. However, this paper elucidates that such physical structural changes will impact on heavy metal ions removal efficiency. This investigation suggests that the type of size reduction in lignocellulosic biosorbent preparation plays a very important role in overall biosorption performance, so it should be carefully considered every time when the mechanical treatment of material is necessary to be applied

Utjecaj ekspozicije krošnje na morfološka svojstva iglica devet četinjača

The aim of this research was to investigate if the crown exposure of some conifers influenced to needle properties. The leaf morphological traits of sixty-six trees of nine conifers: Atlas cedar, Austrian pine, Blue spruce, Douglas fir, European spruce, European yew, Serbian spruce, Silver fir, and White fir, from six Belgrade parks, were analyzed. Five needles were measured from each of the four main crown exposures. Length, width, area and perimeter of needles were investigated. Species, parks in which they were found, as well as crown exposures, differed mostly in needle length and needle width. Correlations between measured needle traits were determined by linear regression analysis. Strong positive correlations were found between the length, perimeter, and area of needles. The differences among the species in terms of light requirement determine species for individual planting as light-loving or partial shade species (Atlas cedar, European spruce, Serbian spruce, Blue spruce, Austrian pine and Douglas fir), or for group planting as shade-loving species (Silver fir, White fir and European yew).Analizirano je 66 stabala devet vrsta četinjača: atlaskog cedra, crnog bora, bodljikave smreke, duglazije, obične smreke, šumske tise, Pančićeve omorike, koloradske  jele i obične jele, iz šest beogradskih parkova. Analizirano je pet iglica sa svake od četiri glavne ekspozicije krošnje. Ispitivana je duljina, širina, površina i opseg iglica. Vrste, parkovi u kojima su pronađene, kao i ekspozicije njihovih kruna, razlikovali su se po duljini i širini iglica. Korelacije između izmjerenih svojstava iglica određene su linearnom regresijskom analizom. Utvrđene su jake pozitivne korelacije između duljine, opsega i površine iglica. Razlike među vrstama u zahtjevima za svjetlom određuju vrste za pojedinačnu sadnju kao vrste koje vole svjetlo ili polusjenu (atlaski cedar, obična smreka, Pančićeva omorika, bodljikava smreka, crni bor i duglazija) ili za grupnu sadnju kao sjenoljubne vrste (obična jela, dugoigličava jela i šumska tisa)

The Effect of Glycol Derivatives on the Properties of Bio-Based Unsaturated Polyesters

The scope of the present study was to prepare fully bio-based unsaturated polyester resins (UPRs) with comparable properties to the commercial formulations. The focus was set on the determination of the optimal prepolymer formulation using the same set of diacids (itaconic and succinic acid) and different diols (propylene glycol, isosorbide and neopentyl glycol) or its equimolar mixtures, keeping the fixed molar ratio of 1:1:2.1 in all feed compositions. Instead of commonly used styrene, bio-based dimethyl itaconate was used as a reactive diluent (RD). The rheology of the obtained resins was studied in detail. The effect of the used diol on structural (FTIR), thermal (DSC), thermomechanical (DMA), and mechanical (tensile) properties was explained. The properties of UPRs were found to be highly dependent on the diol used in the prepolymer formulation. The UPR with an equimolar ratio of propylene glycol and neopentyl glycol was shown to be the most promising candidate to compete with the commercial petroleum-based resins

Spektralno ispitivanje soli alkalnih elemenata 12-volframfosforne kiseline

In this paper the latest results of our continuing investigation of heteropoly acids and their salts are reported. Specially attention was paid to the influence of cations on the dynamic equilibrium of protonic species, as well as on the structure of the host lattice itself, i.e., the Keggin anions. The investigations were done by IR and Raman spectroscopy within the range of 1200-40 cm-1.U ovom radu saopšteni su poslednji rezultati naših sistematskih ispitivanja heteropolikiselina i njihovih soli. Posebna pažnja posvećena je uticaju katjona na dinamičku ravnotežu protonskih vrsta, kao i na strukturu kristalne rešetke, odnosno Keginovih anjona. Ispitivanja su vršena metodama infracrvene i ramanske spektroskopije u oblasti 1200-40 cm-1. Dobijeni rezultati su važni za objašnjenje mehanizma provodljivosti, kao i za rešavanje problema praktične primene ovih jedinjenja kao čvrstih elektrolita. PR Projekat Ministarstva nauke Republike Srbije

Activity of a Catalase Enzyme in Plants from the Burned Areas of the Vidlič Mountain Beech Forest

In 2007, a catastrophic fire on the Vidlic Mountain in south-east Serbia occurred. It burned down nearly 1000 ha of forest. Study of biochemical and physiological parameters in plants which inhabit post fire areas and their comparison with control is of essential importance in estimating the impact of fire on plant characteristics and potential applications. After the fire pioneer and indigenous plants from habitats affected by fire have a characteristic metabolism. In this comparative study, the activity of enzyme catalase (ЕC 1.11.1.6, H2 O2 : H2 O2 oxidoreductase) was determined in plant species from a habitat affected by fire and the same plant species from the forest which had not been affected by fire as a control. Assessment of enzyme activity was carried out on the root, leaves and flowers of plant species Geranium macrorrhizum, Doronicum columnae, Aegopodium podagraria, Fagus moesiaca, Tussilago farfara, Glechoma hirsuta, Chelidonium majus and Primula veris. The first group of plant samples used for determination was obtained from the habitat that was affected by fire two years ago. Catalase activity was measured using the gasometric method and the values obtained for this activity were expressed as ml of O2 . The presented results show a significant increase in catalase activity in individuals from habitats affected by fire in relation to the control group. Increased catalase activity is a consequence of oxidative stress caused by chemical changes in soil that were generated by fire.Publishe

Zearalenone and ochratoxin A: adsorption by kaolin modified with surfactant

Octadecyldimethylbenzyl ammonium chloride (OA) was used as a surfactant for the preparation of organokaolin. The natural kaolin (from a plant for production of quartz sand in Rgotina, Serbia) was modified with a surfactant in amount equal to 90% of the kaolin cation exchange capacity (CEC). FTIR spectroscopy was used for characterization of the new product. FTIR spectra confirmed the presence of OA ions at the kaolin surface. Adsorption of mycotoxins – zearalenone (ZEN) and ochratoxin A (OCHRA) was studied by organokaolin at different amounts of adsorbent and pHs. Results showed that the presence of organic cations in the kaolin structure increased adsorption of both ZEN and OCHRA. Adsorption of the mycotoxins by organokaolin increased with increasing amounts of adsorbent and, at the lowest amount of solids in suspension, adsorption of ZEN and OCHRA was slightly higher at pH 7 and 9

Preparation of 90Y-Labeled Tin Fluoride Colloid for Radiosynovectomy

In this study, tin fluoride colloid (SnF-c) was prepared, labeled with 90Y and characterized with respect to its physicochemical properties. Particle size of SnF-c, at constant concentration of SnF2, was dependent on pH, concentration of NaF, temperature and time. The particle size of SnF-c decreased with an increase in NaF concentration and a decrease in reaction mixture pH. Radiolabeling yield of 90Y-SnF-c at higher temperature increased and it was greater than 98% for the preparation at 95 oC. Due to high labeling yield and stability, 90Y-SnF-c might be a promising agent for radiosynovectomy.Physical chemistry 2012 : 11th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 201