1. Sustainable processing of materials using supercritical fluids : doktorska disertacijaDragana Borjan, 2022, doktorska disertacija Opis: Supercritical fluids (SCFs) are powerful solvents with many unique properties. They have great potential for many processes, from extraction to chemical reactions and recycling. Accordingly, phase equilibrium data and thermodynamic and transport properties measurements in systems with a supercritical phase, as well as reliable and versatile mathematical models of the phase equilibrium thermodynamics, are needed for the process design and economic feasibility studies. The dissertation focuses on the benefits of supercritical fluid technology and consists of three main sections.
The first section includes studies of the phase equilibria of the binary gas-alcohol and gas-urea derivatives. The influence of pressure and temperature on the system behaviour (solubility, viscosity, density, interfacial tension, melting point curve) was investigated. Most of the experiments were carried out with a high-pressure optical view cell, with minor modifications of the apparatus and measurement principle to determine mentioned thermodynamic and transport properties.
The second part of the dissertation deals with the recovery of extracts from natural materials. Special interest is oriented towards supercritical fluid extracts, characterised by strong biological activities, especially antimicrobial and antioxidant properties. Supercritical fluid extraction has been performed on a semi-continuous apparatus (at pressures of 150 bar and 250 bar and temperatures of 313.15 K and 333.15 K for oregano extraction; and at pressures of 100 bar and 300 bar and temperatures of 313.15 K and 333.15 K for red beetroot extraction) and various methods such as the microdilution method and the DPPH method were used to determine antimicrobial and antioxidant activity.
In the third part, an overview of different methods for recycling carbon fibre reinforced composites is given, including chemical recycling with supercritical fluids. This field has not been well explored, and the approach is relatively new but very interesting from a sustainable point of view. For an economically feasible process design, the thermodynamic and mass transfer data have to be determined. The principles of the future lab- and pilot-scale operations demand these supporting data be known.
The results obtained in the frame of this study represent the high added value in the scientific field. They are essential to design and modify processes that yield products that cannot be achieved with conventional production processes.
Ključne besede: supercritical fluids, alcohols, urea, phase equilibria, viscosity, density, interfacial tension, modified capillary method, isolation methods, supercritical fluid extraction, pharmacological activity, carbon fiber reinforced composites, recycling techniques
Objavljeno v DKUM: 11.10.2022; Ogledov: 388; Prenosov: 70
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2. Electrodynamics in organic dimer insulators close to mott critical pointMarko Pinterić, David Rivas Góngora, Željko Rapljenović, Tomislav Ivek, Matija Čulo, B. Korin-Hamzić, Ognjen Milat, Branko Gumhalter, Predrag Lazić, Miriam Sanz Alonso, Weiwu Li, Andrej Pustogow, Guilherme Gorgen Lesseux, Martin Dressel, Silvija Tomić, 2018, izvirni znanstveni članek Ključne besede: strongly correlated systems, Mott insulators, quantum spin liquid, dielectric properties, vibrational properties, density functional theory
Objavljeno v DKUM: 27.06.2018; Ogledov: 1287; Prenosov: 419
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3. Shear modulus of a saturated granular soil derived from resonant-column testsH. Patiño, E. Martínez, Jesús González, A. Soriano, 2017, izvirni znanstveni članek Opis: This paper presents the results of 120 determinations of the shear modulus (G) of a saturated granular soil (20–40 Ottawa sand) in different conditions of relative density (Dr), effective consolidation pressure (σ’ c) and level of torsional excitation (Te). The equipment used was a resonant-column apparatus manufactured by Wykeham Farrance and the tests were performed with relative density values of 20, 40, 60 and 80%, effective consolidation pressures of 50, 100, 150, 200, 250 and 300 kPa, and torsional excitations of 0.025, 0.05, 0.1, 0.2 and 0.4 volts (V), leading to shear strains (γ) between 0.002% and 0.023%. The results led to very simple empirical expressions for the shear modulus as a function of the angular strain for different effective consolidation pressures and void-ratio values.
Ključne besede: resonant column, resonant frequency, shear modulus, relative density, effective consolidation pressure, dynamic shear modulus
Objavljeno v DKUM: 18.06.2018; Ogledov: 944; Prenosov: 70
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4. Effect of the initial structure on the behaviour of Chlef sandNoureddine Della, Ahmed Arab, Mostefa Belkhatir, Hanifi Missoum, Claude Bacconnet, Daniel Boissier, 2010, izvirni znanstveni članek Opis: It has been known for many years that initial structure, plays an important part in the results of laboratory testing of natural of silty sands. For this purpose, a series of monotonic undrained triaxial compression tests were carried out on samples composed of Chlef sand with 0.5% non-plastic silt content using two depositional methods (dry funnel pluviation and wet deposition) at different initial relative density (RD= 29%, 50% and 80%). All specimens were subjected to isotropic consolidation of 50 kPa, 100 kPa and 200 kPa. It was found that the initial structure of the soil influences considerably the undrained shear response in terms of maximal deviatoric stress, peak strength and excess pore water pressure.
Ključne besede: liquefaction, sand, dry funnel pluviation, wet deposition, density, deviatoric stress, pore pressure
Objavljeno v DKUM: 11.06.2018; Ogledov: 691; Prenosov: 72
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5. Determining the speed of sound, density and bulk modulus of rapeseed oil, biodiesel and diesel fuelBoban Nikolić, Breda Kegl, Saša Marković, Melanija Mitrović, 2012, izvirni znanstveni članek Opis: Modern tendencies in the development of diesel engines include the operation of the system for injecting diesel fuel at pressures higher than 100 MPa. Knowing the characteristics of liquid fuels such as speed of sound, bulk modulus and density depending on pressure, is important for predicting the behavior of fuel injection systems for diesel engines and optimization of the same. The paper presents an original method and apparatus (device) for determining the speed of sound and density of fluids depending on the pressures. With this method, values of these characteristics for rapeseed oil, biodiesel and conventional diesel fuel at pressures up to 160 MPa are determined. The method is non-destructive, it can also be applied to higher pressures than 160 MPa, as well as other liquid fluids that are used at high pressure - hydraulic oil, for example.
Ključne besede: biodiesel, rapeseed oil, speed of sound, bulk modulus, density, high pressure
Objavljeno v DKUM: 07.07.2017; Ogledov: 938; Prenosov: 340
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6. Determination of pressure losses in hydraulic pipeline systems by considering temperature and pressureVladimir Savić, Darko Knežević, Darko Lovrec, Mitar Jocanović, Velibor Karanović, 2009, izvirni znanstveni članek Opis: Generally accepted methods for calculating pressure losses within flat pipelines, as presented in literature and used in praxis, are based on the Reynolds number, which considers the viscosity and density of fluid, internal pipe friction coefficient, pipe geometry, and oil circulation velocity. Such an approach contains serious inconsequentiality. Namely, only nominal values for viscosity and density are considered in the calculation, which differs substantially from real conditions. It often leads to inaccurate calculations of pressure losses. A numerical model has been developed within the work prescribed in the paper, which takes into account actual changes in density and viscosity under the current oil pressure and temperature in order to overcome the above weaknesses of standard calculation procedures. Such an approach is novel and provides new capacity for an accurate pressure drop analysis of advanced hydraulic systems.
Ključne besede: tlačne izgube, ravne cevi, viskoznost, gostota, temperatura, pressure loss, float pipelines, viscosity, density, temeprature
Objavljeno v DKUM: 11.08.2015; Ogledov: 1053; Prenosov: 70
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7. Temperature and pressure dependence of volumetric properties for binary mixtures of n-heptane and n-octaneDarja Pečar, Valter Doleček, 2007, izvirni znanstveni članek Opis: The densities of n-heptane, n-octane and their binary mixtures were measured at 298.15, 323.15 and 348.15 K and within the pressure range 0.1 to 40 MPa using a vibrating tube densimeter. The reliability of this technique has been verified in our previous works. The partial molar volumes, excess molar volumes, isothermal compressibilities, isobaric thermal expansivities and internal pressures were calculated from the obtained densities. This study presents the dependence of densities, partial molar volumes, excess molar volumes, isothermal compressibilities, isobaric thermal expansivities and internal pressures on composition, temperature and pressure.
Ključne besede: density measurements, partial molar volume, excess molar volume, isothermal compressibility, isobaric thermal expansivity, internal pressure, n-heptane, n-octane
Objavljeno v DKUM: 10.07.2015; Ogledov: 1273; Prenosov: 109
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8. On automorphisms of Banach algebrasMatej Brešar, 2002, izvirni znanstveni članek Opis: Podana je razširitev Jacobsonovega izreka o gostoti na Banachove algebre z avtomorfizmi. Zatem so obravnave aplikacije tega izreka. Med drugim so karakterizirani avtomorfizmi ▫$alpha$▫ na Banachovi algebri z lastnostjo, da je preslikava ▫$alpha-1$▫ spektralno omejena.
Ključne besede: matematika, funkcionalna analiza, teorija operatorjev, avtomorfizem, Banachova algebra, izrek o gostoti, spektralno omejena preslikava, mathematics, functional analysis, operator theory, automorphism, Banach algebra, density theorem, spectrally bounded map
Objavljeno v DKUM: 10.07.2015; Ogledov: 946; Prenosov: 100
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9. Kantorovitz, Shmuel; Piskarev, Serguei: Mean stability of semigroups. - Taiwanese J. Math. 6, no. 1, 89-103 (2002). [ISSN 1027-5487]Miklavž Mastinšek, 2004, recenzija, prikaz knjige, kritika Ključne besede: matematika, teorija operatorjev, ▫$C_0$▫-polgrupe, stabilnost, mathematics, operator theory, ▫$C_0$▫-semigroups, mean stability, range density, weight functions
Objavljeno v DKUM: 10.07.2015; Ogledov: 762; Prenosov: 25
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