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    Wyświetlanie 1-4 z 4
    Tytuł:
    Simulations of a multicomponent mixture in the reflux classifier todemonstrate the effect of dispersion coefficient on its internal state
    Autorzy:
    Syed, Naveedul Hasan
    Khan, Naseer Ahmed
    Habib, Muddasar
    Powiązania:
    https://bibliotekanauki.pl/articles/1449637.pdf
    Data publikacji:
    2020
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    continuum model
    dispersion fluxes
    ecart probable error
    segregation
    slip velocity
    Opis:
    In this study, influence of the dispersion coefficient on the internal state of a multicomponent mixture comprising 35 types of particle species with five different sizes ranging -2.0+0.25 mm and seven different densities, 1400 to 2000 kg/m3, in a reflux classifier under continuous process conditions is presented. Simulations were performed to study the effect of dispersion coefficient on the separation density, D50, separation efficiency, Ep, and solid volume fraction of the multicomponent mixture. The simulation results provided a good agreement with the published experimental results of the reflux classifier, operated at full scale in 2005, for a relatively high value of the dispersion coefficient, 0.0030 m2/s, and a relatively small value of the dispersion, 0.00030 m2/s, in the fluidization and inclined sections of the device, respectively. Moreover, different fixed values of the dispersion coefficient and a published proposed model of the dispersion coefficient were incorporated in the model to examine variations in the system and were compared with the validated simulation results. It was found that the selected values of the dispersion coefficient had not much effect on the $D_{50}$ values. However, the Ep values changed significantly with changes in the dispersion coefficient values. The smaller values of the dispersion coefficient provided lower values of the Ep that did not match well with the validated simulation results. Furthermore, the variations in the total solid volume fraction within the reflux classifier for different values of the dispersion coefficient has been demonstrated.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2020, 56, 1; 76-88
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Simulations of mono-sized solid particles in the reflux classifier under continuous process conditions
    Autorzy:
    Syed, Naveedul Hasan
    Khan, Naseer Ahmed
    Powiązania:
    https://bibliotekanauki.pl/articles/110844.pdf
    Data publikacji:
    2019
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    beneficiation
    fluidized beds
    inclined channel
    segregation
    superficial velocity
    Opis:
    In this study, a fluidized bed separator incorporating inclined channels, the Reflux Classifier (RC), was modeled to describe the transport behavior of mono-sized solid particles using a 2D computational segregation-dispersion model. The model is a volume flux-based model comprising the dispersion and segregation fluxes. Simulations were performed to examine variations in the solid volume fraction of particle species of size 0.163 mm and density 2450 kg/m3 by altering variables such as fluidization velocity, underflow rate and water flux in the feed. The system achieved a maximum solid volume fraction of 0.50 (v/v) near the base at a fluidization velocity 0.00020 m/s, that reduced to 0.20 at the fluidization velocity 0.0060 m/s. Overall, the results showed a decrease in the average solid volume fraction from 0.37 to 0.21 for the corresponding fluidization velocities. Simulation results also successfully demonstrated the capacity of the RC in retaining the solid particles at a superficial fluidization velocity 0.020 m/s, significantly higher than the terminal settling velocity, 0.015 m/s, of the solid particles, due to the presence of an inclined channel. Similarly, with increasing the underflow rate, the average solid volume fraction decreased from 0.29 to 0.055 due to the discharge of a larger quantity of solid particles from the base. Furthermore, a higher concentration of solid particles was observed in the inclined section at lower water flux in the feed stream. Additionally, flux balance calculations were carried out at different points within the RC to ensure the accuracy of the model predictions.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2019, 55, 3; 631-642
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Influence of multi extrusion die process on mechanical and chemical behavior of 2024-T3 alloy
    Autorzy:
    Razooqi, Ahmed Ibrahim
    Abbas, Naseer M.
    Ghazi, Sara Saad
    Powiązania:
    https://bibliotekanauki.pl/articles/2174206.pdf
    Data publikacji:
    2022
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    wyciskanie
    odkształcenie plastyczne
    korozja elektrochemiczna
    Al 2024-T3
    extrusion
    plastic deformation
    electrochemical corrosion
    Opis:
    In this paper, a cold multi-pass extrusion process for a 15mm in diameter solid 2024-T3 aluminum alloy rod was carried out using three dies to obtain three different diameters of 14mm, 13mm, and 12mm. The microstructure, hardness, and corrosion behavior were investigated before and after the extrusion process. Load-Displacement data were recorded during each extrusion process. The electrochemical corrosion test was made in a 3.5 wt.% NaCl solution using potentiostat instrument under static potentials test. Corrosion current was recorded to determine the corrosion rate for specimens. The results showed that the extrusion load increased with the number of extrusion passes, which is also seen in hardness test results. In addition, the corrosion rate decreased with the increase in the number of extrusion passes. This is due to severe plastic deformation, which generates a fine grain structure of (AlCu) and (AlCuMg) components.
    Źródło:
    International Journal of Applied Mechanics and Engineering; 2022, 27, 3; 163--170
    1734-4492
    2353-9003
    Pojawia się w:
    International Journal of Applied Mechanics and Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An assessment of unstimulated salivary flow rate, IgA and clinical oral dryness among active and passive smokers
    Autorzy:
    Nigar, Seeme
    Hassan, Sobia
    Maqsood, Afsheen
    Ahmed, Naseer
    Al-Askar, Mansour
    Mokeem, Sameer A.
    Alqutub, Montaser N.
    Aldahian, Nada
    AlSagob, Eman I.
    AlMubarak, Abdulrahman A.
    Vohra, Fahim
    Abduljabbar, Tariq
    Powiązania:
    https://bibliotekanauki.pl/articles/2085673.pdf
    Data publikacji:
    2022-02-15
    Wydawca:
    Instytut Medycyny Pracy im. prof. dra Jerzego Nofera w Łodzi
    Tematy:
    IgA
    xerostomia
    passive smokers
    active smokers
    salivary flow rate
    oral dryness
    Opis:
    ObjectivesThe aim of this study was to assess the impact of smoking on the whole salivary flow rate (SFR), IgA levels and clinical oral dryness (COD) among active and passive smokers.Material and MethodsThe participants were categorized as active smokers (N = 54) or passive smokers (N = 163). Saliva was collected in tubes and placed in ice storage at –70°C. Salivary IgA levels were assessed in duplication using the enzyme linked immunosorbent assay (ELISA) method. Following the saliva sample collection, the subjects were assessed for COD using the COD score, SFR and caries. Chi-square test, the t-test and ANOVA were employed to compare the clinical impact of the smoking status associated with specific variables (smoking status, number of cigarettes, active caries, gender, age, COD score, IgA level and SFR). A p-value of <0.05 was considered significant.ResultsTwo hundred and seventeen subjects with the mean age of 32.86±6.30 years, with 145 males (66.8%) and 72 females (33.2%), were included in the study. Among the active smokers, 88.8% were males compared to 11.2% females. The active smokers had the mean age of 32.52 years, a COD score of 1.43, an IgA level of 1.39 g/l, and a SFR of 0.37 ml/min. Among the passive smokers, 59.5% were males and 40.5% were females, with the mean age of 32.97 years, a COD score of 0.87 g/l, an IgA level of 1.47, and a SFR of 0.42 ml/min. Active caries showed a positive correlation with the number of cigarettes, with significance in the >35 years age group (p < 0.05).ConclusionsThe study demonstrated significant differences in SFR, IgA and COD scores among the active and passive smokers. The number of cigarettes had a negative impact on saliva production, IgA levels, the oral health status, and the progression of caries with respect to age and gender. Smoking potentially leads to xerostomia associated with active caries.
    Źródło:
    International Journal of Occupational Medicine and Environmental Health; 2022, 35, 1; 39-51
    1232-1087
    1896-494X
    Pojawia się w:
    International Journal of Occupational Medicine and Environmental Health
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-4 z 4

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