140-220 GHz Imaging Front-end Based on 250 nm InP/InGaAs/InP DHBT Process

This paper presents a pre-amplified detector receiver based on a 250 nm InP/InGaAs/InP double heterojunction bipolar transistor (DHBT) process available from the Teledyne scientific. The front end consists of a double slot antenna followed by a five stage low noise amplifier and a detector, all integrated onto the same circuit. Results of measured responsivity and noise are presented. The receiver is characterized through measuring its response to hot (293) and cold (78) K terminations. Measurements of the voltage noise spectrum at the video output of the receiver are presented and can be used to derive the temperature resolution of the receiver for a specific video bandwidth

Limit states of reinforced high strength concrete prefabricated two-chord structures

U ovoj disertaciji izvršena je teorijska i eksperimentalna analiza linijskog montažnog armiranobetonskog nosača sa čeličnim zetegama. Da bi se potvrdile teorijske postavke proračuna, unapredila tehnologija grañenja i omogućilo praćenje ponašanja ovih sistema u svim naponsko-deformacijskim stanjima, izvršena su eksperimantalna istraživanja sa betonom visoke čvrstoće na pritisak. Eksperimentalno su ispitivana i analizirana dva nosača (modela) “A“ i “B“, raspona 20.00 m u prirodnoj veličini koji su izrañeni od betona visokih čvrstoća od 75 MPa i 78 MPa, respektivno. U uvodnom delu je navedeno da ovakvi nosači u velikoj meri zadovoljavaju zahteve savremene tehnologije grañenja u koje spadaju: znatna redukcija sopstvene težine, brza i laka montaža i izbegavanje potreba za betoniranjem na licu mesta. Pored toga, ispunjeni su svi zahtevi u pogledu stabilnosti, funkcionalnosti i trajnosti ovakvih nosača. Kratkotrajno statičko opterećenje, nanošeno je u sedam faza, a osma faza je izvršena tako što je nosač izložen udaru u sleme pod punim opterećenjem sedme faze slobodnim padom tega od 5.00 kN sa visine 6.00m. U poglavlju 2 je prikazan pregled najznčajnijih svojstava betona visoke čvrstoće, metode projektovanja betonske mešavine, pregled radnih dijagrama betona u pojedinim zemljama i njihovo poreñenje sa odgovarajućim analizama. U poglavlju 3 dat je pregled najznačajnijih objekata od betona visoke čvrstoće koji su realizovani u svetu sa osnovnim karakteristikama i recepture za beton na nekim objektima. Pregled primene dvopojasnih sistema, uglavnom u našoj zemlji, prikazan je u poglavlju 4. Ovi konstrukcijski sistemi su nastali i unapreñeni na Grañevinskom fakultetu u Beogradu, što je rezultiralo njihovom velikom primenom u našoj zemlji. Dat je pregled realizovanih objekata sa karakterističnim detaljima autora sa ovog fakulteta i nekih detalja koje je autor disertacije realizovao, sam ili u saradnji sa njima. Peto poglavlje daje opis eksperimentalnih istraživanja: pripremu, izradu probnih mešavina, pravljenje modela u prirodnoj veličini i nanošenje opterećenja sa merenjima opštih i lokalnih deformacija nakon svake faze opterećenja. U šestom poglavlju daje se teorijska analiza ovih dvopojasnih sistema. Izložena je analiza stanja napona i deformacija, zatim analiza graničnih stanja ovih sistema u obliku integro-diferencijalnih jednačina. Ukratko je prikazan jedan metod dvojice kiniskeh autora, koji predstavlja uprošćenje metoda koji su predložili naši autori Ivković, Perišić, Aćić i Pakvor. Izvršena je teorijska analiza ponašanja nosača usled dejstva udara i razvijen je poseban računarski program na bazi konačnih elemenata i uporeñeni mereni i teorijski rezultati koji se dobro slažu. U sedmom poglavlju prikazuje se metodologija odreñivanja faktora graničnog opterećenja koje nosač dovodi u stanje granične ravnoteže za aplicirano i jednako podeljeno opterećenje na gornjem pojasu. Primenjeni postupak odreñivanja faktora graničnog opterećenja i mehanizma loma je zasnovan na dualitetu statičkih i kinematičkih veličina, i primenom linearnog programiranja odreñene karakteristične statičke i kinematičke veličine i formulisani zaključci. Za ova opterećenja je izvršena analiza ponašanja sistema prema teoriji I i II reda za elastično ponašanje nosača. U osmom poglavlju je izvršena završna uporedna analiza, tj. poreñenje teorijskih i eksprimentalnih rezultata i konstatovano njihovo dobro slaganje...In this PhD thesis is carried out theoretical and experimental analysis of linear, prefabricated reinforced concrete structures with a lower steel chord. To confirm the theoretical calculations, improve construction technology and to enable monitoring of the behavior of these systems in all stress-strain states was carried out an experimental research with concrete of high compressive strength. Two girders (models) “A” and “B” are investigated experimentally in lifesize, made of high strengths concrete with a compressive strength 75 MPa and 78 MPa. In the introductory chapter states that these structures largely meet the requirements of modern construction technology which include: significant reduction of its own weight, quick and easy assemblage, avoiding the need for concreting on site, and in addition met all the requirements in terms of stability, functionality and durability of these structural systems. The short-term static load was applied in seven stages, and in the eights stage the ridge of the loaded structure was exposed to the impact of the weight free fall 5.00 kN from a height 6.00 m. In Chapter 2 is given an overview of the most important features of high-strength concrete, methods of concrete admixture design, review of operating diagrams for concrete in certain countries and their comparison with the corresponding analysis. In Chapter 3 is given an overview of the most important buildings constructed of high strength concrete that have been realized in the world with the basic characteristics and admixtures of concrete on some of these buildings. Through Chapter 4 provides an overview of application of two-chord structural systems, mainly in our country. These systems are created and developed in Faculty of Civil Engineering, University of Belgrade, which led to their wide application in our country. The review of the executed projects and characteristic details designed by authors from this faculty and some of the details that the author has realized, either alone or in collaboration with them, is presented. The fifth chapter mostly describes experimental research, preparation, making of test mixtures, creating a life-size models, applying loads with measurements of general and local deformation after each load stage. The sixth chapter gives a theoretical analysis of the two-chord structures. Provides a stress and strain analysis, and then the limit state analysis of the system in the form of integrodifferential equations. One method, given by two Chinese authors, that represents simplification of the method for analysis of these systems, proposed earlier by Ivkovic, Perišić, Aćić and Pakvor, is shortly explained. The seventh chapter presents a methodology for determining the factor of limit load that leads the structural system into a state of limit equilibrium for the applied load and equally distributed load all along upper chord. Procedure for determining the factor of limit load and mechanism of collapse is based on the duality of characteristic static and kinematic quantities. Appling Linear programming these quantities are determined successfully and corresponding conclusion are formulated. For all mentioned loadings, an analysis for elastic behaviour of investigated structures according to the theory of the first and second order is carried out. A comparative analysis, i.e. comparison of theoretical and experimental results, is performed in Chapter 8, and good agreement is found between these results..

Graph energies and their applications

The energy E(G) of a graph G is the sum of absolute values of the eigenvalues of the adjacency matrix of G. This spectral quantity was introduced in 1978 by Ivan Gutman, but its extensive research started only twenty five years later. A large number (over hundred) variants of graph energy have been proposed, based on matrices other than the adjacency matrix. Research of these graph energies is nowadays very active, resulting in well over a thousand publications. In recent years, more than two papers on graph energies appear each week. Graph energies found a remarkable number of various applications. In this paper, we outline some basic, mainly statistical, facts on the research of graph energies, and point out their main applications.Bulletin de l'Académie serbe des sciences. Classe des sciences mathématiques et naturelles. Sciences mathématiques. 44, 152 (2019)

Tomography of fast-ion velocity-space distributions from synthetic CTS and FIDA measurements

We compute tomographies of 2D fast-ion velocity distribution functions from synthetic collective Thomson scattering (CTS) and fast-ion D-alpha (FIDA) 1D measurements using a new reconstruction prescription. Contradicting conventional wisdom we demonstrate that one single 1D CTS or FIDA view suffices to compute accurate tomographies of arbitrary 2D functions under idealized conditions. Under simulated experimental conditions, single-view tomographies do not resemble the original fast-ion velocity distribution functions but nevertheless show their coarsest features. For CTS or FIDA systems with many simultaneous views on the same measurement volume, the resemblance improves with the number of available views, even if the resolution in each view is varied inversely proportional to the number of views, so that the total number of measurements in all views is the same. With a realistic four-view system, tomographies of a beam ion velocity distribution function at ASDEX Upgrade reproduce the general shape of the function and the location of the maxima at full and half injection energy of the beam ions. By applying our method to real many-view CTS or FIDA measurements, one could determine tomographies of 2D fast-ion velocity distribution functions experimentally

Combination of fast-ion diagnostics in velocity-space tomographies:Paper

Fast-ion Dα (FIDA) and collective Thomson scattering (CTS) diagnostics provide indirect measurements of fastion velocity distribution functions in magnetically confined plasmas. Here we present the first prescription for velocity-space tomographic inversion of CTS and FIDA measurements that can use CTS and FIDA measurements together and that takes uncertainties in such measurements into account. Our prescription is general and could be applied to other diagnostics. We demonstrate tomographic reconstructions of an ASDEX Upgrade beam ion velocity distribution function. First, we compute synthetic measurements from two CTS views and two FIDA views using a TRANSP/NUBEAM simulation, and then we compute joint tomographic inversions in velocity-space from these. The overall shape of the 2D velocity distribution function and the location of the maxima at full and half beam injection energy are well reproduced in velocity-space tomographic inversions, if the noise level in the measurements is below 10%. Our results suggest that 2D fast-ion velocity distribution functions can be directly inferred from fast-ion measurements and their uncertainties, even if the measurements are taken with different diagnostic methods