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    Wyświetlanie 1-9 z 9
    Tytuł:
    Flotation separation of scheelite from calcite using sodium polyacrylate as depressant
    Autorzy:
    Zhang, Y.
    Chen, R.
    Li, Y.
    Wang, Y.
    Luo, X.
    Powiązania:
    https://bibliotekanauki.pl/articles/110896.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    scheelite
    calcite
    flotation
    sodium polyacrylate
    selective depression
    Opis:
    The depressing properties of sodium polyacrylate (PA-Na) for calcite from scheelite were studied by microflotation experiments, zeta potentials, X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculation. Flotation results revealed that the selective depression effect of PA-Na was better than that of sodium silicate (Na2SiO3), and PA-Na can depress calcite more effectively than scheelite. The flotation recovery of scheelite and calcite kept at about 75% and 15% respectively at the pulp pH 9.3~9.6 and PA-Na concentration from 37.5 mg/dm3 to 50 mg/dm3. The zeta potentials of the minerals were significantly altered and the zeta potential of calcite became more negative than scheelite. XPS analysis deduced the occurrence of chemisorption between PA-Na and mineral surfaces, and the chemisorption of PA-Na on calcite was stronger than on scheelite. The results from DFT calculation demonstrated that the absolute value of the adsorption energy in the presence of PA-Na on the surface of calcite {104} was larger than on the surface of scheelite {111}. With the combination of the analysis, it could be concluded that calcite was more easily depressed than scheelite, and this finding remarkably matched with the microflotation experimental results. Furthermore, by using PA-Na as depressant, the flotation separation of scheelite from calcite can be achieved by controlling the flotation pH and PA-Na dosage.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2018, 54, 2; 505-516
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Image compression-encryption algorithm combining compressive sensing with log operation
    Autorzy:
    Chen, R.-L.
    Zhou, Y.
    Luo, M.
    Zhang, A.-D.
    Gong, L.-H.
    Powiązania:
    https://bibliotekanauki.pl/articles/174009.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    image encryption
    image compression
    compressive sensing
    log operation
    Opis:
    Based on compressive sensing and log operation, a new image compression-encryption algorithm is proposed, which accomplishes encryption and compression simultaneously. The proposed image compression-encryption algorithm takes advantage of not only the physical realizability of partial Hadamard matrix, but also the resistance of the chosen-plaintext attack since all the elements in the partial Hadamard matrix are 1, –1 or log 1 = 0. The proposed algorithm is sensitive to the key and it can resist various common attacks. The simulation results verify the validity and reliability of the proposed image compression-encryption algorithm.
    Źródło:
    Optica Applicata; 2018, 48, 4; 563-573
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Monte Carlo based angular analysis of multiple scattered photons for underwater optical imaging
    Autorzy:
    Li, S.
    Wang, R.
    Chen, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/173322.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    underwater imaging
    turbid media
    Monte Carlo method
    multiple scattering
    Opis:
    Image contrast and visibility associated with underwater optical imaging systems are usually degraded by the absorbing and scattering effects of turbid waters. To improve the image contrast, laser-range-gate has been widely applied to underwater optical imaging systems. The work of Katsev et al. (Appl.Opt. 38(33), 1999, pp. 6849–6858) shows that the contrast of a shadow image is greater than that of the object image. The present paper outlines a Monte Carlo based simulation method of image formation for underwater optical imaging. It is found that the contrast of a shadow image varies with gate starting depths. The angular distribution of multiply scattered photons is obtained via semi-analytical models (Shengfu Li et al., Opt.Commun. 381, 2016, pp. 43–47). The simulated results show that increasing the gate starting depth can reduce the highly backscattered photons, thus can improve the image contrast.
    Źródło:
    Optica Applicata; 2018, 48, 2; 237-247
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Mass transfer process of leaching weathered crust elution-deposited rare earth ore with magnesium salts
    Autorzy:
    Chen, Z.
    Zhang, Z.
    He, Z.
    Chi, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/110343.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    mass transfer
    magnesium salts
    theory plate
    weathered crust elution-deposited rare earth ore
    Opis:
    In order to optimize the leaching process of weathered crust elution-deposited rare earth ore with magnesium salts, the influence of different flow rate, concentration of magnesium ions, initial pH of magnesium salts solution and experimental temperature on the mass transfer process of rare earth and aluminum was investigated in the case of using magnesium salts as leaching agent. The relationship between the flow rate μ and the HETP (Height Equivalent of Theoretical Plate) is in accordance with the Van Deemter equation when magnesium salts were used as leaching agent. The optimum condition for rare earth and aluminum were 0.4 cm3/min of flow rate and 0.2 mol/dm3 of magnesium ion concentration of magnesium sulfate, magnesium chloride and magnesium nitrate respectively. Under this condition the mass transfer efficiency of rare earth and aluminum with three kinds of magnesium salts follow the order of Mg(NO3)2>Mg(Cl)2>MgSO4. High temperature contributes to improving the mass transfer efficiency of rare earth and aluminum. Magnesium nitrate as the leaching agent can get the highest leaching mass transfer efficiency of rare earth and magnesium sulfate as the leaching agent can make the impurity leaching and mass transfer efficiency of Al is the lowest.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2018, 54, 3; 1004-1013
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Preparation of activated bentonite and its adsorption behavior on oil-soluble green pigment
    Autorzy:
    Zheng, R.
    Gao, H.
    Ren, Z.
    Cen, D.
    Chen, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/110655.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    activated bentonite
    acid activation
    microwave heating
    oil-soluble green pigment
    adsorption
    Opis:
    The present research work focuses on effective preparation of activated bentonite (AB) and its application in removal of oil-soluble green pigment (OSGP) from either vegetable oils or food-processing wastewater. Mono-factor experiments were carried out to explore the effects of operation factors in preparation of AB. The parameters investigated were the effect of contact time, adsorbent dosage, initial OSGP concentration and temperature. The chemical composition, crystalline phases, microstructure and functional groups of prepared AB were characterized and evaluated by X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR), respectively. The adsorption kinetics and equilibrium isotherms were studied, finding that the adsorption process fitted better with the pseudo-second-order model and the Freundlich isotherm equation. In addition, thermodynamic parameters, such as standard the Gibbs free energy (ΔG°), standard enthalpy (ΔH°) and standard entropy (ΔS°) were also calculated, indicating that adsorption was spontaneous and endothermic. The findings of this investigation suggest that AB prepared through microwave activation as a cheap adsorbent holds great potential to remove oil-soluble green pigment in the wastewater treatment process.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2017, 53, 2; 829-845
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of modified starch on separation of fluorite from barite using sodium oleate
    Autorzy:
    Chen, Z.
    Ren, Z.
    Gao, H.
    Qian, Y.
    Zheng, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/109938.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    fluorite
    barite
    modified starch
    flotation
    Opis:
    In this study, a modified starch was utilized to selectively separate barite from fluorite. The results of flotation tests showed that highly selective separation of fluorite from barite was obtained when 250 mg/dm3 of modified starch and 13.16×10−5 mol/dm3 sodium oleate was used in neutral solutions. FTIR spectra results showed that the modified starch can adsorb on the fluorite and barite surfaces. Zeta potential analyses indicated that the modified starch had little effect on adsorption of sodium oleate on the fluorite surface, although it interfered with the adsorption of sodium oleate on the barite surface. Contact angle measurements results corresponded well with the flotation results.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2018, 54, 2; 228-237
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Use of nanofiltration membranes to concentrate and recover leached aluminum from acidified water treatment sludge
    Autorzy:
    Cheng, W. P.
    Chen, P. H.
    Tian, D. R.
    Yu, R. F.
    Fu, C. H.
    Powiązania:
    https://bibliotekanauki.pl/articles/208030.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    water purification
    nanofiltration
    acidic solutions
    leaching
    roztwory kwaśne
    oczyszczanie wody
    nanofiltracja
    ługowanie
    glin
    Opis:
    The recovery of aluminum from water purification sludge is usually performed by making the solution acidic or basic. However, for economic reasons and reasons of safety, excessive doses of acid or base should not be utilized. Accordingly, the aluminum concentration in the leached solution is typically limited, thus the recovered aluminum cannot be directly reused as a coagulant. A nanofiltration (NF) membrane can be used in the acidic solution to concentrate high-valence metal ions. There-fore, in this work, H2SO4 was utilized to leach Al3+ ions from water purification sludge. Then, the Al3+ ion solution was concentrated using a low-price NF membrane. The effect of natural organic matter on the Al3+ ion concentrating efficiency in the filtration process has been elucidated. Experimental results reveal that Al3+ ions were effectively prevented from passing through the NF membrane, enabling a highly concentrated aluminum solution to be obtained. However, the presence of organic compounds may reduce the efficiency of the concentration of Al3+ ions in the solution.
    Źródło:
    Environment Protection Engineering; 2016, 42, 3; 19-32
    0324-8828
    Pojawia się w:
    Environment Protection Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Generation of chirped microwave signal with any central frequency based on a nonuniformly spaced finite impulse response filter
    Autorzy:
    Chen, D.
    Wang, R.
    Pu, T.
    Xiang, P.
    Fang, T.
    Zheng, J.
    Xiong, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/174334.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    microwave photonics
    microwave photonic filter
    chirped microwave signal
    dual drive Mach–Zehnder modulator
    Opis:
    A novel optical approach to generating a chirped microwave signal by using a nonuniformly spaced finite impulse response filter is proposed and demonstrated. In this scheme, a narrowband Gaussian pulse is used as the original chirped-free signal, which is easy to be acquired. To eliminate the need of a wideband chirped-free signal, a mixer and a radio frequency signal are used to up-convert the spectrum of the original Gaussian signal. Therefore, the required frequency response can be calculated and reconstructed by a finite impulse response filter with nonuniformly spaced taps. Besides, a dual drive Mach–Zehnder modulator is used to realize single sideband modulation of the chirpedfree signal. Thus, the transfer function induced by the fiber dispersion is eliminated and the chirped microwave signal with any central frequency can be generated. In this paper, a design example of a filter with a central frequency of 10GHz is provided, and generation of the target chirped microwave signal is also demonstrated by numerical simulations.
    Źródło:
    Optica Applicata; 2016, 46, 3; 399-408
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dispersion-compensating en/decoder for a time-spreading/wavelength-hopping optical code-division multiplexing (OCDM) system
    Autorzy:
    Zheng, J.
    Wang, R.
    Pu, T.
    Lu, L.
    Fang, T.
    Su, Y.
    Li, L.
    Yang, Q.
    Chen, X.
    Powiązania:
    https://bibliotekanauki.pl/articles/174365.pdf
    Data publikacji:
    2013
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    optical code-division multiplexing (OCDM)
    fiber Bragg grating (FBG)
    dispersion
    Opis:
    A novel dispersion-compensating fiber Bragg grating (FBG)-based en/decoder is proposed to compensate both the out-band and in-band dispersion in a time-spreading/wavelength-hopping (TS/WH) optical code-division multiplexing (OCDM) system. The experimental realization of such en/decoders only needs a uniform-pitch phase mask and a sub-micrometer precision moving stage. Such an en/decoder pair with the ability of compensating the dispersion of transmission in 20-km single mode fiber (SMF) is simulated and experimentally fabricated. Both the simulation and experimental results show that the decoded pulse can be recovered without any distortion owing to the elimination of dispersion.
    Źródło:
    Optica Applicata; 2013, 43, 3; 485-495
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-9 z 9

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