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    Wyświetlanie 1-12 z 12
    Tytuł:
    Analysis of frequency-controlled induction motor at higher than rated frequencies and a constant stator voltage
    Autorzy:
    Firago, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/1813847.pdf
    Data publikacji:
    2013
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    induction motor
    frequency control
    constant load torque
    constant load power
    rating power
    Opis:
    A technique for calculation of characteristics of an induction motor operating under conditions: the constant load torque or constant load power at frequencies higher than rated ones and the rated stator voltage is presented. For the mode of constant load power the analytical solution of frequency-controlled induction motor electric drive transients is obtained.
    Źródło:
    Prace Naukowe Instytutu Maszyn, Napędów i Pomiarów Elektrycznych Politechniki Wrocławskiej. Studia i Materiały; 2013, 69, 33; 30--43
    1733-0718
    Pojawia się w:
    Prace Naukowe Instytutu Maszyn, Napędów i Pomiarów Elektrycznych Politechniki Wrocławskiej. Studia i Materiały
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The influence of activity coefficient and equilibrium constant models on the speciation of aqueous solutions of H2SO4–MgSO4–Al2(SO4)3 at 235 and 250 °C
    Autorzy:
    Dickson, Okechukwu Vincent
    Deleau, Thomas
    Coquelet, Christophe
    Espitalier, Fabienne
    Lombart, Julien
    Tardy, Antoine
    Powiązania:
    https://bibliotekanauki.pl/articles/24085644.pdf
    Data publikacji:
    2023
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    activity coefficient
    equilibrium constant
    hydrometallurgy
    speciation
    thermodynamics
    Opis:
    Supersaturation occurs in many industrial applications promoting reactive crystallisation between the reactants to form solutes. These solutes accumulate during precipitation, leading to the formation of scales on the inner walls of the reactor and particularly around the stirrer, causing modifications in the hydrodynamics. This encrustation is responsible for process shutdowns in continuous crystallisation processes. Supersaturation control is essential for industrial processes aimed at controlling or inhibiting the formation of these solids. Knowledge of mineral solubility and chemical speciation is required to account for the composition of the complexes in the system in their various solid or aqueous forms. This speciation is obtained by considering the thermodynamic equilibrium constants of the dissociation/complexation reactions involved in the system, the pressure, and the activity coefficients of the chemical species in their molecular or electrolyte form. From these thermodynamic quantities and the state of the system, we can predict the direction of the reaction. This study highlights the risk of the lack of experimental information on equilibrium constants at high temperatures and moderate pressures. Our goal is to evaluate the accuracy of existing models classically used to predict the equilibrium constant in such very hard conditions encountered in hydrometallurgical processes. Furthermore, we demonstrate the influences of equilibrium constants estimation and activity coefficient models on the speciation of H2SO4–Al2(SO4)3–MgSO4 systems, forming hydronium alunite and kieserite in the laterite liquor of hydrometallurgical processes.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2023, 59, 5; art. no. 167497
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electrochemical deposition of cobalt-nickel coatings in a constant magnetic field
    Autorzy:
    Miękoś, Ewa
    Klepka, Tomasz
    Zieliński, Marek
    Sroczyński, Dariusz
    Powiązania:
    https://bibliotekanauki.pl/articles/2146891.pdf
    Data publikacji:
    2022
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    cobalt-nickel coatings
    constant magnetic field
    electrochemical deposition
    Opis:
    The electrochemical deposition of Co-Ni coatings on gold-disc electrode with and without of constant magnetic field (CMF) has been investigated using cyclic voltammetry (CV), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The EDX results showed that CMF applied during the electrodeposition of Co-Ni coatings affects their composition. In particular, an increase by 17% in the content of cobalt in coating, i.e. the main component, with a simultaneous decrease of nickel content has been observed when magnetic induction B of 1200 mT was applied compare to this without of CMF. Moreover, it has been supposed that the increase of internal stresses in electrodeposited Co-Ni coatings under CMF can be attributed to a decrease in their thickness.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2022, 58, 2 (Special issue - selected papers conference: Physicochemistry of interfaces - instrumental methods); art. no. 146066
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A conceptual flotation circuit for fine coal processing based on combination of the tree analysis and kinetic data
    Autorzy:
    Ranjbar, Mohammad
    Bazmandeh, Mehdi
    Powiązania:
    https://bibliotekanauki.pl/articles/24085755.pdf
    Data publikacji:
    2023
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    kinetic rate constant
    tree analysis
    conceptual design
    flotation
    coal
    Opis:
    In this research study, we focus on the tree test results as well as the first-order kinetic model to evaluate flotation test data to propose a conceptual design of a flotation circuit for a specific coal sample. Results from the tree test showed it was possible to achieve a product with ash content less than 10% with 8% as combustible recovery and indicated for this coal sample, to obtain low ash – low recovery condition. Kinetic test results showed some of the streams had the same constant, so it could combine streams with similar rates according to configuration aspects. The proposed circuit includes stages (1- rougher, 2- rougher -scavenger, 3- cleaner, 4- cleaner -scavenger, and 5-recleaner) and recleaner concentrate indicated as the final product and rougher -scavenger tailings and cleaner -scavenger tailings also indicated as a final tailing. It is worth noting the proposed circuit is a conceptual design, so the validation of data on a larger scale for the obtainment of the optimized circuit is crucial.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2023, 59, 3; art. no. 167948
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Proposition of a bubble-particle attachment model based on DLVO van der Waals and electric double layer interactions for froth flotation modelling
    Autorzy:
    Buchmann, Markus
    Öktem, Gülce
    Rudolph, Martin
    Boogaart, K. Gerald van den
    Powiązania:
    https://bibliotekanauki.pl/articles/2146873.pdf
    Data publikacji:
    2022
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    attachment
    froth flotation
    Hamaker constant
    surfactants
    collectors
    hydrophobic interaction
    Opis:
    The attachment of bubbles and particles represents one of the sub-processes in froth flotation among others (e.g. collision and detachment). The main interactions present at short distances in such a bubble-particle system are the van der Waals and electrostatic double layer interactions combined in the DLVO theory. In this study, the special features of the attachment process were discussed with a focus on flotation. For the van der Waals interactions, the Hamaker constants were calculated with the help of Lifshitz´ macroscopic theory as a function of the separation distance for specific material combinations. A specific material system (PbS-Water-Air) was used to demonstrate the implementation of bubble-particle attachment of the proposed modelling framework. The effects of additional surfactant/collector and air layers on the solid interface were presented. This framework of layered systems showed that the sign of van der Waals interaction could be turned from repulsive to attractive without the need to extend the DLVO theory. The thickness of the layer as a function of collector adsorption between a particle and a bubble is suggested as a modelling parameter in bubble-particle attachment efficiency.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2022, 58, 5; art. no. 154812
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Analysis of chromite processing plant data by first order autoregressive model
    Autorzy:
    Tasdemir, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/109877.pdf
    Data publikacji:
    2013
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    time series
    autoregressive model
    time constant
    process control
    chromite processing
    Opis:
    Many mineral processing data can be monitored by a time series model. This research presents results of analysis and simulations of a chromite processing plant data determined by time series model. The plant data obtained by shift to shift include feed grade, concentrate grade, tailing grade, Cr/Fe ratio in concentrate. All the chromite processing data were found stationary over time. The autocorrelation was high for feed grade and Cr/Fe ratio. Weaker autocorrelation was observed for concentrate grade and tailing grade. Autoregressive integrated moving average (ARIMA, 1,0,0) or first order autoregressive (AR, 1) model, was found to fit all data very well. The models obtained have been also shown to be used for the near future estimation of these data. The time constant which is an indicator of sampling frequency of the data sets were determined. It was found that sampling frequency was enough for concentrate and tailing grade and their original values can be used in process control charts for monitoring. On the other hand, the sampling frequency should be reduced for feeding grade and Cr/Fe ratio for the same aims hence ARIMA residual charts were more suitable to monitor their values.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2013, 49, 1; 157-174
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Kinetics of flotation. Order of process, rate constant distribution and ultimate recovery
    Autorzy:
    Bu, X.
    Xie, G.
    Peng, Y.
    Ge, L.
    Ni, C.
    Powiązania:
    https://bibliotekanauki.pl/articles/110034.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    kinetic mode
    kinetic order
    rate constant distribution
    ultimate recovery
    overfitting
    Opis:
    Kinetic models can be used to characterize the flotation process. In this paper, three primary parameters, namely, distribution of flotation rate constant f(K), order of flotation process n and ultimate recovery R∞ are presented to perform analysis of flotation kinetics. The flotation rate constant f(K) is a function of both the size and hydrophobicity of particles. Though the more commonly used distributions are Delta function as well as Rectangular, Kelsall and Gamma models, there is no agreement in the literature as to which distribution function better characterize the floatability distribution. The first-order models can be used to describe most mineral flotation processes, while there is also evidence that the non-integral-order equation is capable of representing the kinetic characteristics of the batch flotation process. The order is lower than 1 in the initial moments of the flotation process. The solution of ultimate recovery calculated by the least squares method is greater than 100% (R∞ >100%). An empirical model was proposed to avoid the improper phenomenon in the solution of ultimate recovery, which can improve the availability and validity of kinetic models. Finally, more attention should be paid to the overfitting resulting from the increase in the number of parameters in the statistical analysis of kinetic models.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2017, 53, 1; 342-365
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Changes in the flotation kinetic of bituminous coal before and after natural weathering processes
    Autorzy:
    Xia, W.
    Peng, Y.
    Ren, C.
    Xie, G.
    Liang, C.
    Powiązania:
    https://bibliotekanauki.pl/articles/951864.pdf
    Data publikacji:
    2015
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    flotation kinetic
    classical first-order rate constant
    natural weathering processes
    XPS
    contact angle
    Opis:
    Natural weathering processes can make coal surface more hydrophilic due to the increase of content of hydrophilic functional groups (C-O, C=O, and COOH) and the decrease of content of hydrophobic functional groups (C-C and C-H) on coal surface, and hence the flotation recovery of fine coal is reduced. In this paper, a series of flotation tests were conducted in order to investigate the changes in the flotation kinetic of bituminous coal before and after natural weathering processes. Additionally, XPS was used to indicate the changes in surface properties of bituminous coal. In the investigations the flotation kinetic was changing. The classical first-order rate constant (k) of bituminous coal flotation was reduced after the natural weathering processes. A relationship between the classical first-order rate constant (k) and the hydrophilicity ability (HA) was given.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2015, 51, 2; 401-410
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Propagation in dielectric rectangular waveguides
    Autorzy:
    Yeap, K. H.
    Teh, K. H.
    Yeong, K. C.
    Lai, K. C.
    Loh, M. C.
    Powiązania:
    https://bibliotekanauki.pl/articles/173566.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    dielectric rectangular waveguide
    transverse wave numbers
    attenuation coefficient
    surface impedance
    propagation constant
    fundamental mode
    Opis:
    We present a fundamental and accurate approach to compute the attenuation of electromagnetic waves propagating in dielectric rectangular waveguides. The transverse wave numbers are first obtained as roots of a set of transcendental equations developed by matching the fields with the surface impedance of the wall. The propagation constant is found by substituting the values of transverse wave numbers into the dispersion relation. We have examined the validity of our model by comparing the computed results with those obtained from Marcatili’s equations and the finite element method. In our results, it is shown that the fundamental mode is identical with that found in a perfectly conducting waveguide. Our analysis also shows that a hollow waveguide is found to have much lower attenuation than its dielectric counterparts. Since the cutoff frequency is usually affected by the constitutive properties of the dielectric medium, for a waveguide designed for wave with the same cutoff frequency, hollow waveguides turn out to be relatively larger in size.
    Źródło:
    Optica Applicata; 2016, 46, 2; 317-330
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electrical neutralization ability of polyaluminum chloride (PACl) coagulants with different OH–/Al3+ ratios by fluorescence quenching effect
    Autorzy:
    Chi, Fung Hwa
    Cheng, Wen Po
    Yu, Ruey Fang
    Chen, Zhao Feng
    Powiązania:
    https://bibliotekanauki.pl/articles/207968.pdf
    Data publikacji:
    2020
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    stała Sterna-Volmera
    polichlorek glinu
    kwas humusowy
    fluorescencja
    Stern-Volmer constant
    polyaluminum chloride
    humic acid
    fluorescence
    Opis:
    The electrical neutralization ability of polyaluminum chlorides (PACls) with respect to humic acid was investigated by the fluorescence quenching method. The Stern–Volmer constant (Kq) at various pH and coagulation doses was determined for polyaluminum chlorides (PACl-B) of various basicities (B, B = [OH–]/[Al]). The experimental results show that under acidic conditions, the order of Kqvalues of PACl-B is PACl-2.5 > PACl-2.3 > PACl-1.5 > AlCl3. In solutions of pH = 7, the order of Kqvalues is PACl-1.5 > PACl-2.3 > PACl-2.5 > AlCl3. When pH > 7, aluminum ions are rapidly hydrolyzed, thus PACls of various basicities generally do not show capacity for electrical neutralization with humic acid. At pH = 6, all PACls-B obtain the maximum Kq values, indicating that humic acid and PACl-Bcoagulation process is less affected by H+ or OH– ions, and produces the best electrical neutralization ability. Compared to the past method of using surface potential as a means of determining the ability of neutralization of coagulation, the results of this study show that the Kq value of the quenching effect can reduce the experiment complexity.
    Źródło:
    Environment Protection Engineering; 2020, 46, 2; 25-39
    0324-8828
    Pojawia się w:
    Environment Protection Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The analysis of the effect of wrought wire clasps on the conditions of abutment teeth
    Autorzy:
    Kasperski, J
    Chladek, G.
    Płonka, Ł.
    Powiązania:
    https://bibliotekanauki.pl/articles/307034.pdf
    Data publikacji:
    2013
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    wrought wire clasp (WWC)
    wear
    removable partial denture
    spring constant
    zużycie zębów
    sprężyna wielokrotna
    wyjmowana proteza częściowa
    Opis:
    Laboratory evaluation of spring constants (k) of wrought wire clasps (WWC) separated from removable partial denture (RPD) and the results of tibological tests which represent the dependence of enamel wear with normal force have been presented in the paper. The results of laboratory examinations have been combined with the results of clinical assessment of the level of abutment teeth wear. On the basis of the examinations performed it has been revealed that the following factors have the greatest impact on tribological wear of abutment teeth: the time of using RPD and the normal force exerted by WWC on abutment tooth. Normal force depends to a great extent on the place of contact of WWC with the tooth. It has also been found that abutment teeth featuring higher scale of wear are more loosened. The diameter of wire used for making WWC, total length of the arm and k determined for the total length of the arm did not have any impact upon the scale of wear of abutment teeth.
    Źródło:
    Acta of Bioengineering and Biomechanics; 2013, 15, 1; 27-33
    1509-409X
    2450-6303
    Pojawia się w:
    Acta of Bioengineering and Biomechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The comparative study of influence of lactic and glycolic acids copolymers type on properties of daunorubicin loaded nanoparticles and drug release
    Autorzy:
    Nikolskaya, E.
    Sokol, M.
    Faustova, M.
    Zhunina, O.
    Mollaev, M.
    Yabbarov, N.
    Tereshchenko, O.
    Popov, R.
    Severin, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/307136.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    nanocząsteczki
    daunorubicyna
    PLGA
    uwalnianie kontrolowane
    stała dysocjacji
    nanoparticles
    daunorubicin
    controlled release
    MCF7/MCF7 Adr
    dissociation constant
    Opis:
    The aim of this study was to compare the physico-chemical and biological properties of polymeric nanoparticles obtained from poly(DL-lactide-co-glycolide) (PLGA) with different ratios of monomers loaded with daunorubicin (DNR). Methods: DNR-loaded nanoparticles (NPs) were prepared with use of modified simultaneous double-emulsion solvent evaporation/diffusion technique. NPs were characterized using dynamic light scattering, atomic force microscopy, transmission electron microscopy, scanning electron microscopy, and differential scanning calorimetry and Fourier transform infrared spectroscopy. Results: NPs with DNR were differing in size and zeta potential, depending on the type of polymer. The data obtained show that total content of DNR correlates with the values of the binding constant of DNR with polymers. The release of DNR from NPs proceeds predominantly for polymers with lower binding constants. The in vitro study of NPs on the MCF-7 cells showed similar activity of particles and substances while for the anthracycline-resistant MCF-7Adr cells the cytotoxicity of the nanoparticles was 3 to 7 times higher depending on the type of copolymer. Conclusions: PLGA DNR-loaded nanoparticles can be used to overcome multidrug resistance (MDR) as well as for reducing the frequency of DNR reception due to the prolonged effect, which allows maintaining the concentration of the drug at the required level. The usefulness of binding constant calculations for obtaining nanoparticles with the maximum drug loading was proven. The rate of drug administration and the frequency of administration can be calculated based on the DNR release profiles and release parameters that depend on polymer type.
    Źródło:
    Acta of Bioengineering and Biomechanics; 2018, 20, 1; 65-77
    1509-409X
    2450-6303
    Pojawia się w:
    Acta of Bioengineering and Biomechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-12 z 12

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