1. A Sustainable Route From Quartz to Bifunctional Material with Adsorbed Lanthanides for Enhanced Fluorescent Activation in Doxycycline SensingO. Semeshko, Maksym Fizer, Valeriia V. Sliesarenko, Jaroslav Briančin, Oleksandr Bondarchuk, Aleksandra Lobnik, Inna V. Melnyk, 2024, original scientific article Abstract: A nanosized bifunctional adsorbent with diamino and phenyl groups on its surface is synthesized through the functionalization of silica derived from quartz. The composition, morphology, and particle size of the functionalized silica are characterized using various physicochemical methods. The material demonstrates high sorption properties for La(III) and Ce(III), both found in Ni-MH batteries, as well as Eu(III). The synthesized functionalized silica, with adsorbed lanthanides, is employed for sensor-based detection of doxycycline in aqueous solutions.
Keywords: Lanthanides, adsorption, doxycycline sensing, ethylenediamine groups, phenyl groups, quartz, rare earth ions, silica particles, nanosized bifunctional adsorbent, functionalization of silica, sensor-based detection
Published in DKUM: 27.08.2025; Views: 0; Downloads: 2
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2. Assessment of the Capability of Magnetic Nanoparticles to Recover Neodymium Ions from Aqueous SolutionAna Ambrož, Irena Ban, Thomas Luxbacher, 2022, original scientific article Abstract: Magnetic nanoparticles (MNPs) have received increasing attention for various applications due to their fast synthesis, versatile functionalization, and recyclability by the application of a magnetic field. The high surface-to-volume ratio of MNP dispersions has suggested their use as an adsorbent for the removal of heavy metal ions. We investigated the applicability of MNPs composed of a maghemite core surrounded by a silica shell functionalized with aminopropylsilane, γ-Fe2O3-NH4OH@SiO2(APTMS), for the removal of neodymium ions (Nd3+) from aqueous solution. The MNPs were characterized for their size, composition, surface functionality and charge. Despite of the promising properties of MNPs, their removal from the aqueous dispersion with an external magnet was not sufficient to reliably quantify the adsorption of Nd3+ by UV-Vis spectroscopy.
Keywords: rare earth elements, maghemite, nanoparticles, UV-Vis spectroscopy, adsorption
Published in DKUM: 08.08.2023; Views: 476; Downloads: 276
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3. Removal of neodymium ions from aqueous solution by magnetic nanoparticles : magistrsko deloAna Ambrož, 2021, master's thesis Abstract: This work is focused on the synthesis and characterization of surface-functionalized
γ-Fe2O3-NH4OH@SiO2(APTMS) nanoparticles, their applications, and performance for Nd3+ removal from aqueous solutions, with an emphasis on the characterization of MNPs and Nd(NO3)3•6H2O.
The γ-Fe2O3 nanoparticles were obtained by the co-precipitation method, stabilized with ammonia solution, and functionalized by SiO2 and APTMS. Neodymium nitrate hexahydrate (Nd(NO3)3•6H2O) used in aqueous solution was synthesised from neodymium oxide (Nd2O3) powder. The thermal behaviour and stability of the magnetic nanoparticles and Nd(NO3)3•6H2O was studied with thermogravimetric analysis (TGA) in O2, N2, and air atmosphere. Transmission electron microscopy (TEM) images were obtained in order to analyse the particle morphology and measure the size distribution of the nanoparticles. The hydrodynamic diameter of particles and the zeta potential were measured to determine the stability of particles in the solution. ATR-FTIR spectroscopy was used to confirm the functionalization of the magnetic nanoparticles and the adsorption of Nd3+ ions. The effect of the REE adsorption on the MNPs was studied by comparing the sample’s UV-Vis absorption spectra.
The laboratory testing and analysis of the results indicate promising applications for the removal of the REE from aqueous solutions with magnetic nanoparticles. However, the coating of the MNP core by SiO2(APTMS) is inefficient for the removal of Nd3+ ions.
Keywords: Magnetic nanoparticles, Rare earth elements, Neodymium, Adsorption, Zeta potential, UV-Vis spectroscopy
Published in DKUM: 03.05.2021; Views: 1570; Downloads: 164
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4. Numerical study of the dynamic active lateral earth pressure coefficient of cohesive soilsMehrab Jesmani, Hossein Alirezanejad, Hamed Faghihi Kashani, Mehrad Kamalzare, 2017, original scientific article Abstract: Retaining walls are proposed in many projects, such as bridges, coastal structures, road constructions and wherever lateral support is required for the vertical surface of an excavation. The active lateral pressure coefficient of soil, Ka , is an important parameter for studying the static and dynamic behaviors of these retaining walls. Many studies have evaluated this coefficient in static situations, but in most previous dynamic studies, researchers have worked on the behavior of cohesionless backfill soil or made simplifying assumptions (e.g., pseudo-static status) for cohesive soils as backfill soil. In this study, the size of the active lateral earth pressure coefficient (Ka) was studied in a full dynamic situation (Kae). A retaining wall with cohesive backfill soil is evaluated using the finite-difference method (FDM) and the effects of important soil and loading properties are assessed. The model is based on Mohr-Coulomb failure criteria under seismic loading. The results show that the value of Kae at the top of the wall, where it is highly sensitive to any variation in the soil and loading properties, is greater than one due to the high pressure value induced by the horizontal dynamic acceleration and the presence of tension cracks.
Keywords: dynamic active lateral earth pressure coefficient (Kae), cohesive backfill soil, finite difference method (FDM), tension cracks, retaining wall, seismic loading
Published in DKUM: 18.06.2018; Views: 1549; Downloads: 122
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5. Evaluation of dynamic soil pressures acting on rigid culverts : shaking-table testsDeniz Ulgen, Mehmet Yener Özkan, 2016, original scientific article Abstract: The seismic safety of underground structures (culvert, subway, natural-gas and water-sewage systems) plays a major role in sustainable public safety and urban development. Very few experimental data are currently available and there is no generally accepted procedure to estimate the dynamic pressures acting on these underground structures. This study aims to enhance the state of the prevalent information necessary to understand the dynamic behaviour of box culverts and the stresses acting under dynamic excitations through experimental analyses. For this purpose, a series of shaking-table tests were conducted on box-type culverts buried in dry sand. To simulate the free-field boundary conditions, a laminar box was designed and manufactured for use with a 1-g shake table. Two culvert models having different rigidities were tested under various harmonic motions in order to examine the effect of the flexibility ratio on dynamic lateral soil pressures. Based on the test results, a simplified dynamic pressure distribution acting on the sidewalls of the culvert model was suggested. Then, a dynamic lateral coefficient was defined for the proposed peak pressure value in the distribution. The values of this coefficient were obtained as a function of the shear strain by considering the relative stiffness between the soil and the underground structure.
Keywords: box culvert, dynamic earth pressure, shaking table, dynamic soil-structure interaction, laminar box, dynamic lateral coefficient
Published in DKUM: 18.06.2018; Views: 1000; Downloads: 236
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6. Evaluation of the plastic critical depth in seismic active lateral earth pressure problems using the stress-characteristics methodAmin Keshavarz, 2016, original scientific article Abstract: The plastic critical depth or the conventional tension crack depth has a considerable effect on the active lateral earth pressure in cohesive soils. In this paper the depth for c-ϕ soils has been evaluated in the seismic case using the stress-characteristics or slip-line method. The plastic critical depth was calculated on the basis of the theory of the stress-characteristics method and by considering the horizontal and vertical pseudo-static earthquake coefficients. The proposed solution considers the line of discontinuity in the stress-characteristics network. The earth slope, wall slope, cohesion and friction angle of the soil and the adhesion and the friction angle of the soil-wall interface were considered in the analysis as well. The results show that the plastic critical depths of this study are smaller than those of the other methods and are closer to the modified Mononobe-Okabe method. The effects of the wall and the backfill geometry, the mechanical properties of the soil and the pseudo-static coefficients were studied.
Keywords: plastic critical depth, stress characteristics, active lateral earth pressure, seismic
Published in DKUM: 15.06.2018; Views: 1371; Downloads: 129
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7. The limit values and the distribution of three-dimensional passive earth pressuresStanislav Škrabl, 2008, original scientific article Abstract: This paper presents a novel approach to the determination of the critical distribution and limit values of three-dimensional passive soil pressures acting on flexible walls following the upper-bound method within the framework of the limit-analysis theory. The method of limit analysis with a set of three-dimensional kinematically admissible hyperbolic translational failure mechanisms is used to determine the critical distribution of the passive pressures along the retaining structurećs height. The intensity of thepassive pressures is gradually determined with the mentioned translational failure mechanisms in the top-down direction. Thus, the critical distribution,the trust point and the resultant of the passive pressures that can be activated at the limit state for the chosen kinematic model are obtained. The results of the analyses show that the total sum of passive pressures, considering the critical distribution, is lower than the comparable values published in the literature. Furthermore, the trust point of the passive pressure resultant is independent of the friction between the retaining structures and the soil.
Keywords: limit analysis, earth pressure, passive pressure, failure surface, soil-structure interaction
Published in DKUM: 05.06.2018; Views: 1160; Downloads: 170
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8. Determination of passive earth pressure using three-dimensional failure mechanismHelena Vrecl-Kojc, Stanislav Škrabl, 2007, original scientific article Abstract: This paper presents a modified three-dimensional (3D) failure mechanism for determining the 3D passive earth pressure coefficient using the upper bound theorem within the framework of the limit analysis theory. The translational kinematically admissible failure mechanism generalized with a depth of h = 1.0 is considered in the analysis. The mechanism geometry presents a volume of rigid blocks composed of the central body and two lateral rigid bodies, which are connected by a common velocity field. The front surface of the central body interacts with the retaining wall, while the upper surface can be loaded by surcharge loading. The lateral body segments represent four- and three-sided polygons in the cross section of the central body; therefore, they define the polygonal failure surface of the central part. At the outer side, each segment of the lateral body is bounded by infinitesimally spaced rigid half-cones that describe the envelope of a family of half-cones. The numerical results of 3D passive earth pressure limit values are presented by non-dimensional coefficients of passive earth pressure influenced by the soil weight Kpg and a coefficient of passive earth pressure influenced by the surcharge Kpq. This research was intended to improve the lowest values obtained until now using the limit analysis theory. The results are presentedin a graphical form depending on the geometrical parameters and soil properties. A brief description of two world-recognized failure mechanisms based on the limit analysis approach, and the comparison of three failure mechanism results are also presented.
Keywords: soil mechanics, passive earth pressure, upper bound theorem, optimization, three-dimensional failure mechanism
Published in DKUM: 18.05.2018; Views: 1324; Downloads: 76
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9. Interactional approach of cantilever pile walls analysisStanislav Škrabl, 2006, original scientific article Abstract: This paper proposes a new method for the geomechanical analysis and design of cantilever retaining structures. It is based on the limit equilibrium method, but it uses some additional conditions for interaction between the retaining structure and the ground, when referring to the distribution of the mobilized earth pressures on the structure. The greatest benefit of the proposed method is shown in the analysis of structures of layered ground (heterogeneous above the dredge level and homogeneous below it), embedded in frictional and cohesive materials, and in the possibility of considering the influence of surcharge loadings on the active or passive side of the retaining structure. When analyzing such cases in practice, the proposed method gives results which are in better agreement with the results of FEM based elasto-plastic interaction analyses than with the results of currently used methods. At the same time, its results are in accordance with those published for homogeneaus cohesionless ground. Since in practice almost all retaining structures are erected in layered ground (heterogeneaus above the dredge level and homogeneous below it), the proposed method is very convenient and applicable for the analyses and design of cantilever structures under arbitrary geomechanical conditions.
Keywords: geomechanics, soil-structure interaction, retaining walls, embedment, cantilevers, earth pressure, pressure distribution, friction soil - wall, limit analysis, shear forces
Published in DKUM: 17.05.2018; Views: 1460; Downloads: 98
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10. RAZVOJ SISTEMA ZA 3D VIZUALIZACIJO EVAKUACIJSKEGA NAČRTA V GOOGLE EARTHMatic Luznar, 2012, undergraduate thesis Abstract: V diplomskem delu obravnavamo možnost predstavitve lastnih 3D-objektov v okolju Google Earth, ki je hitro rastoča in razvijajoča se programska oprema, dostopna širokemu krogu uporabnikov in je le-tem omogočeno dodajanje lastnih vsebin. V okviru diplomskega dela smo poustvarili model realnega okolja v 3D, ki služi kot prototip okolja, kjer bi se zaradi krizne situacije lahko izvajala evakuacija. V povezavi z označevalnim jezikom KML lahko v Google Earthu dodajamo objekte in na različne načine označujemo ter opisujemo lokacije. Zaradi zamudnosti ročnega opisovanja objektov s KML-jem smo raziskali možnost uvoza že generiranih tridimenzionalnih objektov v Google Earthu. Za potrebe evakuacije smo določili evakuacijsko pot v izbranem okolju. Ustvarjen je bil vmesnik, ki omogoča kreiranje oziroma uvoz koordinat evakuacijske poti in vizualizacijo gibanja po tej poti.
Keywords: spletna rešitev, objekti, evakuacijske poti, Google Earth, KML
Published in DKUM: 09.10.2012; Views: 1976; Downloads: 150
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