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    Wyświetlanie 1-6 z 6
    Tytuł:
    A discussion on the optimality of bulk entry queue with differentiated hiatuses
    Autorzy:
    Vadivukarasi, Manickam
    Kalidass, Kaliappan
    Powiązania:
    https://bibliotekanauki.pl/articles/2175843.pdf
    Data publikacji:
    2022
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    differentiated hiatus time
    steady state probability
    waiting-time distribution
    optimization of expenses
    Opis:
    We consider Markovian differentiated hiatuses queues with bulk entries. With the help of the matrix geometric method, we discuss the stability condition for the existence of the steady-state solution of our model and we obtain the stationary system size by using a probability generating function. The stochastic decomposition form of stationary system size and the waiting time distribution of an arbitrary beneficiary are also analysed. Furthermore, we perform the expense analysis using the particle swarm optimization technique and we obtain the optimality of service rate and hiatus rate. Finally, we study the effects of changes in the parameters on some important performance measures of the system through numerical observations.
    Źródło:
    Operations Research and Decisions; 2022, 32, 2; 137--150
    2081-8858
    2391-6060
    Pojawia się w:
    Operations Research and Decisions
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modeling and simulation of vertical roller mill using population balance model
    Autorzy:
    Fatahi, Rasoul
    Barani, Kianoush
    Powiązania:
    https://bibliotekanauki.pl/articles/1449686.pdf
    Data publikacji:
    2020
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    vertical roller mill
    modeling
    simulation
    cement grinding
    residence time distribution
    Opis:
    There are few studies concerning the process simulation of vertical roller mills (VRMs). In this research work, the application of population balance model for simulation of a VRM in a cement clinker grinding circuit was investigated. The residence time distribution (RTD) was measured, and the tank-in-series and Weller models were employed to describe the residence time distribution. Two sampling surveys were carried out on the VRM circuit. The data from the first survey were used for model calibration, and the specific breakage rates were back-calculated. The model parameters obtained were used for simulation of the second survey, and validation of the model. The results showed that the clinker particle spent a short time inside the VRM and the mean residence time is about 67s. The tanks-in series model compares to Weller model was more proper to describe the residence time distributions in the VRM. The simulation results showed that the specific breakage rates increased with increasing particle size. However, the particles larger than 25.4 mm particles sizes are too large to be properly nipped by master rollers. Finally, it can be concluded that the grinding process of the VRM is very well-predictable with the population balance model.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2020, 56, 1; 24-33
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Discussion on the transient behavior of single server Markovian multiple variant vacation queues
    Autorzy:
    Vadivukarasi, Manickam
    Kalidass, Kaliappan
    Powiązania:
    https://bibliotekanauki.pl/articles/2099427.pdf
    Data publikacji:
    2022
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    Markovian queue
    multiple variant vacations
    transient solution
    waiting-time distribution
    Opis:
    We consider an M/M/1 queue where beneficiary visits occur singly. Once the beneficiary level in the system becomes zero, the server takes a vacation at once. If the server finds no beneficiaries in the system, then the server can take another vacation after the return from the vacation. This process continues until the server has exhaustively taken all the J vacations. The closed form transient solution of the considered model and some important time-dependent performance measures are obtained. Further, the steady state system size distribution is obtained from the time-dependent solution. A stochastic decomposition structure of waiting time distribution and expression for the additional waiting time due to the presence of server vacations are studied. Numerical assessments are presented.
    Źródło:
    Operations Research and Decisions; 2021, 31, 1; 123--146
    2081-8858
    2391-6060
    Pojawia się w:
    Operations Research and Decisions
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A sensitivity analysis of kinetic characterizations in continuous flotation circuits under moderate deviations with respect to perfect mixing
    Autorzy:
    Vinnett, Luis
    Pino-Muñoz, Catalina A.
    Yianatos, Juan
    Díaz, Francisco
    Henríquez, Felipe
    Powiązania:
    https://bibliotekanauki.pl/articles/2146941.pdf
    Data publikacji:
    2022
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    flotation kinetics
    residence time distribution
    perfect mixing
    flotation rate distribution
    industrial flotation circuit
    Opis:
    This paper studies the effect of moderate deviations with respect to perfect mixing on the estimated kinetic parameters in industrial flotation banks. Radioactive tracer tests and mass balance surveys were performed to characterize the mixing regimes and Cu kinetic responses. For three models (Single Rate Constant, Rectangular and Gamma), two approaches to incorporate the residence time distributions (RTD) in the kinetic characterizations of rougher banks were compared: (i) RTDs measured from the radioactive tracer tests; and (ii) pure perfect mixing in each flotation machine. The measured RTDs did not present significant bypass in the evaluated banks. In all cases, comparable model fitting was obtained with both RTD approaches, which indicates that the kinetic models add sufficient flexibility to compensate for moderate biases in the mixing regime. The studied kinetic models showed non-significant differences in the estimated maximum recoveries (R∞), mean (kmean) and median (k50) rate constants when comparing the process modelling from measured RTDs and pure perfect mixing. However, the Gamma model was more sensitive to the RTD assumption in terms of the shapes of the flotation rate distributions. From the results, kinetic characterizations focused only on model fitting, or on R∞ and kmean (or k50) estimations have low sensitivity to the assumption of perfect mixing when the RTDs present moderate deviations with respect to this regime. Special attention must be paid when characterizing floating components as the perfect mixing assumption may bias the shapes of the flotation rate distributions.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2022, 58, 5; art. no. 152420
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Introducing key advantages of intensified flotation cells over conventionally used mechanical and column cells
    Autorzy:
    Hassanzadeh, Ahmad
    Safari, Mehdi
    Khoshdast, Hamid
    Güner, Mustafa K.
    Hoang, Duong H.
    Sambrook, Tim
    Kowalczuk, Przemyslaw B.
    Powiązania:
    https://bibliotekanauki.pl/articles/2146874.pdf
    Data publikacji:
    2022
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    pneumatic flotation cells
    energy input
    mean particle retention time
    fine particles
    bubble size distribution
    Opis:
    The present paper introduces the key advantages of ImhoflotTM, JamesonTM, and RefluxTM flotation cells over the conventionally used mechanical and column cells from different perspectives. The impact of slurry mean retention time, bubble size distribution, and energy input was studied for all cell types. The mean retention time of laboratory scale ImhoflotTM (V030-cell) and RefluxTM flotation cells (RFC100) were measured experimentally using KCl as a tracer. Also, initially a statistical and practical overview of previously installed ImhoflotTM, and JamesonTM cells was presented in this work. It was found that more industrial data is available for the JamesonTM cell. The diagnostic results showed that RefluxTM, JamesonTM, and ImhoflotTM functionally operate similarly based on providing intensive turbulence in the downcomer. They were initially applied to the Australian and the UK coal industries and installed in the cleaning stage of flotation circuits, while there are now more applications in a wide variety of minerals across the world in different flotation stages. First pilot trials on a Russian gold ore were reported operating both JamesonTM and ImhoflotTM cells at the rougher-scalper and cleaner stages providing superior results using the ImhoflotTM cell as rougher-scalper and the JamesonTM at the cleaner. Formation of sub-micron and micron-sized bubbles, effective hydrodynamic characteristics, and low capital and operating costs were reported as major advantages of intensified flotation cells over the conventionally used ones in improving the recoverability of ultra-fine particles. Literature data showed that these cells provide greater gas-hold-up values (40-60%) over the mechanical (5-20%) and column cells (5-25%) with substantially lower power inputs. It was indicated that low mean slurry retention time could lead to a potential enhancement in their throughputs, but further industrial measurements are required to prove this statement. The RefluxTM cell showed a plug-flow mixing regime, while ImhoflotTM V-Cell followed the trend of perfect mixing and plug-flow dispersion regimes.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2022, 58, 5; art. no. 155101
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Routine forecasting of the daily profiles of hourly water distribution in cities. An effectiveness analysis
    Autorzy:
    Cieżak, W.
    Cieżak, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/206970.pdf
    Data publikacji:
    2015
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    forecasting
    multilayer neural networks
    neural networks
    time series
    water supply systems
    water distribution
    prognozowanie
    wielowarstwowe sieci neuronowe
    sieci neuronowe
    szereg czasowy
    wodociągi
    dystrybucja wody
    Opis:
    Sample results have been oresented of verifying three groups of methods of forecasting the time series of short-duration water distributions in city water grids. The analysis covered: ARIMA class models, the time series exponential smoothing methods and artificial neural networks. Since chronological sequences of observations from the immediate past were analyzed, the adopted models did not take any external variables into account. The forecasting errors in the case of multilayer perceptron neural networks were found to be comparable or smaller than the errors of prediction by the ARIMA class models and by the methods of the exponential smoothing of time series.
    Źródło:
    Environment Protection Engineering; 2015, 41, 2; 179-186
    0324-8828
    Pojawia się w:
    Environment Protection Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-6 z 6

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