Wyniki wyszukiwania - Biblioteka Nauki

1

No cutoff for circulants : an elementary proof

100%

Abrams A. , Landau H. , Pommersheim J. , Babson E. , Landau Z.

Probability and Mathematical Statistics

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2022

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tom Vol. 42, Fasc. 1

97--108

EN

We give an elementary proof of a result due to Diaconis and Saloff-Coste (1994) that families of symmetric simple random walks on Cayley graphs of abelian groups with a bound on the number of generators never have sharp cutoff. Here convergence to the stationary distribution is measured in the total variation norm. This is a situation of bounded degree and no expansion; sharp cutoff (or the cutoff phenomenon) has been shown to occur in families such as random walks on a hypercube (Diaconis, 1996) in which the degree is unbounded as well as on a random regular graph where the degree is fixed, but there is expansion (Diaconis and Saloff-Coste, 1993).

2

Investigation of mixing time in liquid under influence of rotating magnetic field

88%

Przybył A. , Rakoczy R. , Konopacki M. , Kordas M. , Drozd R. , Fijałkowski K.

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tom 38

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nr 4

3

Zastosowanie metody elektrochemicznej w reaktorach zbiornikowych do oceny czasu mieszania

88%

Broniarz-Press L. , Woziwodzki S. , Dryjer S.

Inżynieria i Aparatura Chemiczna

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2002

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tom Nr 4

41-42

PL

W pracy przedstawiono wyniki badań eksperymentalnych oceny zjawisk przepływowych w mieszalnikach przy wykorzystaniu pomiarów zmian przewodnictwa elektrolitycznego roztworów wodnych i konduktometru CX—731. Wykazano, że zwiększenie liczby mieszadeł na wale do dwóch pozwala uzyskać lepsze warunki hydrodynamiczne, zmiana liczby mieszania w zależności od liczby Reynoldsa jest nieznaczna.

EN

In the paper the results of the experimental studies performed for the evaluation of flow phenomena in mixers using the conductometer CX-731 and the method of changes in electrolytic conductivity of aqueous solutions have been presented. It has been shown that the multiplication of the agitators mounted on common drive shaft permits to obtain better hydrodynamical conditions and for two agitators the change of mixing number related to the Reynolds number is negligible. Key words: mixing time, effect of agitator number, electrochemical method

4

Pumping capacities and suspending effect of axial agitators

88%

Seichter P. , Pesl L. , Medek J.

Inżynieria i Aparatura Chemiczna

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2002

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tom Nr 4

118-120

EN

Pumping efficiency comprising power input and flowrate data for several axial impellers were investigated and compared. The suspension agitation was investigated as well. The results obtained have shown that the use of hydrofoil agitators can bring significant progress.

5

Agitation efficiency of different physical systems

75%

Karcz J. , Szoplik J. , Major-Godlewska M. , Cudak M. , Kiełbus-Rapała A. , Karcz J. , Szoplik J. , Major-Godlewska M. , Cudak M. , Kiełbus-Rapała A.

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nr 2

6

Studies of a mixing process induced by a rotating magnetic field with the application of magnetic particles

75%

Rakoczy R. , Kordas M. , Markowska-Szczupak A. , Konopacki M. , Augustyniak A. , Jabłońska J. , Paszkiewicz O. , Dubrowska K. , Story G. , Story A. , Ziętarska K. , Sołoducha D. , Borowski T. , Roszak M. , Grygorcewicz B. , Dołęgowska B. , Rakoczy R. , Kordas M. , Markowska-Szczupak A. , Konopacki M. , Augustyniak A. , Jabłońska J. , Paszkiewicz O. , Dubrowska K. , Story G. , Story A. , Ziętarska K. , Sołoducha D. , Borowski T. , Roszak M. , Grygorcewicz B. , Dołęgowska B.

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nr 2

7

Czas mieszania w niestandardowych mieszalnikach zaopatrzonych w kilka mieszadeł

75%

Broniarz-Press L. , Woziwodzki S. , Dulska D.

Inżynieria i Aparatura Chemiczna

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2004

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tom Nr 3s

19-20

EN

In this paper the power consumption, mixing time and mixing efficiency in a non-standard vessel equipped with various impellers have been investigated. The measurements of mixing time and power consumption were performed in water using turbine and disc impellers. It has been shown that mixing time depends strongly on the distance between impellers for multiple systems and on the clearance between a single impeller and tank bottom.

8

Analysis of liquid blending dynamics with Maxblend impellers by Electrical Resistance Tomography

75%

Iwasawa S. , Kubo H. , Takenaka K. , Pintus S. , Maluta F. , Montante G. , Paglianti A.

Chemical and Process Engineering

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2021

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tom Vol. 42, nr 3

197-–207

EN

The aim of the investigation was liquid mixing time measurement in a laboratory scale stirred tank equipped with a metal Maxblend impeller and comparison with the corresponding mixing time obtained with other conventional impellers. The data are collected by Electrical Resistance Tomography, whose applicability in this case is non-trivial, because of the electrical interferences between the large paddles of the impeller and the measuring system. The raw data treatment methodology purposely developed for obtaining the homogenization dynamics curve is presented. A robust approach for a fine and low cost investigation of the mixing performances of close-clearance impellers in opaque systems is suggested. The analysis of the local and averaged conductivity time traces reveals the effect of important variables, such as the fluid viscosity and the vessel configuration, on the mixing time under various agitation conditions. The data collection and post processing procedures open the way to the application of the technique to multiphase and non-Newtonian fluids stirred with close-clearance impellers.

9

Analiza wpływu mieszania na właściwości fizykochemiczne roztworów wodnych saponin uzyskiwanych w procesie ich wielokrotnego uwalniania z orzeszków piorących

75%

Broniarz-Press L. , Dulska D. , Szaferski W.

Przemysł Chemiczny

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2011

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tom T. 90, nr 9

1625-1627

10

Badania hydrodynamiki w kolumnie air-lift z zewnetrzna cyrkulacja płynu

75%

Szoplik J. , Stelmasińska P.

Inżynieria i Aparatura Chemiczna

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2015

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tom Nr 6

360--361

PL

Analizowano udział gazu zatrzymanego w cieczy w strefie wznoszenia i opadania, prędkość cieczy w strefie wznoszenia i opadania oraz czas mieszania w kolumnie air-lift z zewnętrzną cyrkulacją płynu. Badano układy woda-powietrze oraz roztwór gliceryny-powietrze dla różnych objętościowych strumieni powietrza. Wykazano, że w zakresie przeprowadzonych pomiarów typ układu ciecz-gaz miał wpływ na prędkość cieczy w strefie wznoszenia i opadania oraz czas mieszania, a nie wpływał istotnie na wielkość udziału gazu zatrzymanego w cieczy.

EN

The gas hold-up and liquid velocity in a riser and downcomer as well as mixing time in the external-loop airlift reactor were analyzed. Two systems: air – water and air – glycerol in water solution for various volumetric gas flow rates were investigated. It was proved that in the range of performed measurements a type of gas – liquid phase affects the liquid velocity in a riser and downcomer and mixing time but does not significantly affects gas hold-up.

11

Mixing time of the shear-thinning fluids in the agitated vessel

75%

Broniarz-Press L. , Woziwodzki S.

Polish Journal of Chemical Technology

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2006

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tom Vol. 8, nr 4

50-52

EN

The paper deals with the results of experiments on the mixing phenomena in a vessel with different impellers. The flat-bottomed vessel was equipped with Rushton turbines, six flat blade turbines and six pitched down blade turbines. The mixing time related to both, the vessel construction and the rheological properties of the liquid stirred, has been analyzed. The best impeller-tank system, taking into account the process efficiency, has been proposed.

12

Badania czasu mieszania w mieszalniku z niecentrycznie zabudowanym mieszadłem

75%

Karcz J. , Szoplik J.

Inżynieria Chemiczna i Procesowa

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2001

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tom T. 22, z. 3C

651--656

PL

Zbadano wpływ ekscentryczności e/R wału mieszadła na czas mieszania tm cieczy niutonowskiej w mieszalniku o średnicy D = 0.7 m zaopatrzonym w mieszadło śmigłowe. Badania wykazały, że w mieszalnikach, dla których e/R = 0.43 - 0.57, J= 0 oraz e/R = 0, J= 4, czasy mieszania są porównywalne.

EN

The effect of the eccentricity e/R of the impeller shaft on the mixing time tm of the Newtonian liquid agitated by means of the propeller in the vessel of inner diameter D = 0.7 m was studied. The measurements proved that mixing times are comparable in the agitated vessels, for which e/R = 0.43 - 0.57, J — 0 and e/R = 0, J = 4.

13

Dobór mieszadeł do mieszania wybranych cieczy nieniutonowskich

75%

Sierzputowski A. , Paszek E.

Inżynieria i Aparatura Chemiczna

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2002

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tom Nr 4

121-123

PL

W pracy przedstawiono wyniki pomiarów czasu mieszania i mocy mieszania różnych odmian mieszadeł ślimakowych pracujących w dyfuzorze i bez i na podstawie tych badań zaproponowano mieszadło do zastosowania w skali przemysłowej w celu skrócenia czasu mieszania z 8 do ok. 3,5 godzin.

EN

A screw agitator with a draught tube for mixing non-Newtonian liquids in industrial mixers has been selected. Application of the proposed screw agitator enabled the reduction of mixing time from 8 to 3.5 hours.

14

Evaluation of Mixing Efficiency and How it Affects the Properties of the New Green Sand Mixtures

63%

Kielar Š. , Bašistová M. , Lichý P.

Archives of Foundry Engineering

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2023

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tom Vol. 23, iss. 3

88--93

EN

The current trend in the preparation of green sand mixtures emphasizes the acceleration of the mixing process while maintaining the quality of the mixture. This requirement results in the necessity of determining the optimal conditions for mixing the mixture with a given mixer. This work aims to determine the optimal mixing conditions for the newly introduced eddy mixer LM-3e from the company Multiserw-Morek in the sand laboratory at the Department of Metallurgical Technologies, Faculty of Materials and Technology, VŠB - Technical University of Ostrava. The main monitored properties of mixtures will be green compressive strength and moisture of the mixture. The measured properties of the mixture mixed on the eddy mixer will be compared with the properties of the mixture mixed on the existing LM-2e wheel mixer. The result of the experiment confirmed that the eddy mixer is suitable for the preparation of a mixture of the same quality as the wheel mixer but with a significantly reduced mixing time.

15

Czas mieszania w micelarnych roztworach środków powierzchniowo czynnych dla mieszadeł trubinowych

63%

Broniarz-Press L. , Różańska S. , Różański J.

Inżynieria i Aparatura Chemiczna

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2009

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tom Nr 1

86-87

PL

W pracy przedstawiono wyniki badań nad czasem mieszania kationowych środków powierzchniowo czynnych w mieszalniku wyposażonym w mieszadła turbinowe o różnej konstrukcji. W badaniach zastosowano kationowe środki powierzchniowo czynne: bromek tetradecylotri-metyloamoniowy oraz chlorek heksadecylotrimetyloamoniowy. Jako dodatek wspomagający proces asocjacji micelarnej zastosowano salicylan sodu.

EN

The results of studies on the mixing time for cationic surfactant solutions in an agitated vessel equipped with turbine impellers of different construction are presented in the paper. Aqueous solutions of cationic surfactant such as tetradecyltrimethylammonium bromide and hek-sadecyltrimethylammonium chloride wen' used in measurements. Sodium salicylate was applied as an additive promoting the micellar association process.

16

High flow, low shear impellers versus high shear impellers; dispersion of oil drops in water and other examples

63%

Pacek A. W. , Nienow A. W.

Chemical and Process Engineering

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2021

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tom Vol. 42, nr 2

77–-90

EN

Flow patterns generated by two ChemShear impellers, CS 2 and CS 4 have been measured and flow numbers calculated; Fl = 0.04 for both impellers. Transient and equilibrium drop sizes, d32 μm of 3 different viscosity silicone oils agitated by a high-shear Rushton turbine, RT, a low-shear, high-flow HE3 impeller and the two ChemShears were determined. The equilibrium d32 are correlated for all impellers, by d32 = 1300(εT )−0.58 max.svv0.14 with an R2 = 0.94. However, the time to reach steady state and the equilibrium size at the same specific power do not match the above descriptors of each impeller’s characteristics. In other literature, these descriptors are also misleading. In the case of mixing time, a high shear RT of the same size as a high flow HE3 requires the same time at the same specific power in vessels of H/T = 1. In bioprocessing, where concern for damage to cells is always present, free suspension animal cell culture with high shear RTs and low-shear impellers is equally effective; and with mycelial fermentations, damage to mycelia is greater with low shear than high. The problems with these descriptors have been known for some time but mixer manufacturers and ill-informed users and researchers continue to employ them.

17

Charakterystyki mieszania podczas odlewania stali przy użyciu sześciowylewowej kadzi pośredniej

63%

Jowsa J. , Merder T. , Bogusławski A. , Mendrek A.

Hutnik, Wiadomości Hutnicze

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2005

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tom Vol. 72, nr 7-8

377-383

PL

Kadź pośrednia stanowi nieodzowny element procesu ciągłego odlewania stali. Konstrukcja i geometria obiektu decydują o warunkach hydrodynamicznych przepływającej stali. Warunki te kształtują proces przejściowego mieszania stali oraz w różnym stopniu wpływają na proces flotacyjnego usuwania wtrąceń niemetalicznych. Charakterystyka ruchu metalu i procesu mieszania może być odwzorowana przez krzywe typu F i E. Krzywe E i F stanowią prezentację graficzną rozkładów czasu przebywania znacznika w kadzi pośredniej w zależności od przyjętej metody badawczej. Dla kadzi sześciootworowej o pojemności 15 Mg podjęto badania teoretyczne oraz przemysłowe zmierzające do opracowania charakterystyk rozkładu czasu przebywania (F, E). Wyniki badań posłużyły także do zweryfikowania modelu matematycznego przepływu stali w kadzi, opartego na rozwiązaniu równania Naviera-Stokesa. Otrzymane charakterystyki pozwalają na oszacowanie wielkości udziałów poszczególnych rodzajów przepływu cieczy, a w szczególności przepływu idealnego mieszania i przepływu tłokowego.

EN

The tundish is a necessary element of continuous steel casting process. The desing and geometry of this facility determine the hydrodynamic conditions of flowing steel. These conditions shape the transient process of steel mixing and influence in different grade the process of nonmetallic inclusion removal by flotation. The characteristics of mixing process can be represented by curves of F and E types. For a six-way tundish of a capacity of 15 Mg theoretical studies and industrial tests were undertaken for developing characteristics of the distribution of residence time (F, E). The investigation results were used also for verifying the mathematical model of steel flow in the tundish based on the Navier-Stokes equation. The obtained characteristics enable the estimation of the quantity of volume fraction of separate types of liquid flow and in particular the ideal mixing and the plug flow.

18

Strong stationary duality for Möbius monotone Markov chains : examples

63%

Lorek P. , Szekli R.

Probability and Mathematical Statistics

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2016

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tom Vol. 36, Fasc. 1

75--97

EN

We construct strong stationary dual chains for nonsymmetric random walks on square lattice, for random walks on hypercube and for some Ising models on the circle. The strong stationary dual chains are all sharp and have the same state space as original chains.We use Möbius monotonicity of these chains with respect to some natural orderings of the corresponding state spaces. This method provides an alternative way to study mixing times for studied models.

19

Studies of a mixing process induced by a rotating magnetic field with the application of magnetic particles

63%

Rakoczy R. , Kordas M. , Markowska-Szczupak A. , Konopacki M. , Augustyniak A. , Jabłońska J. , Paszkiewicz O. , Dubrowska K. , Story G. , Story A. , Ziętarska K. , Sołoducha D. , Borowski T. , Roszak M. , Grygorcewicz B. , Dołęgowska B.

Chemical and Process Engineering

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2021

|

tom Vol. 42, nr 2

157-–172

EN

We demonstrate in this study that a rotating magnetic field (RMF) and spinning magnetic particles using this kind of magnetic field give rise to a motion mechanism capable of triggering mixing effect in liquids. In this experimental work two mixing mechanisms were used, magnetohydrodynamics due to the Lorentz force and mixing due to magnetic particles under the action of RMF, acted upon by the Kelvin force. To evidence these mechanisms, we report mixing time measured during the neutralization process (weak acid-strong base) under the action of RMF with and without magnetic particles. The efficiency of the mixing process was enhanced by a maximum of 6.5% and 12.8% owing to the application of RMF and the synergistic effect of magnetic field and magnetic particles, respectively

20

Charakterystyka strefy przejściowej kadzi pośredniej typu "delta"

63%

Mender T. , Jowsa J. , Wierzcha M. , Misiak A.

Hutnik, Wiadomości Hutnicze

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2007

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tom Vol. 74, nr 8

398-402

PL

W artykule przedstawiono analizę warunków hydrodynamicznych i przejściową strefę mieszania dla przemysłowej kadzi pośredniej typu "delta". Dla oceny warunków kształtowania się przejściowej strefy mieszania przeprowadzono badania zmiany stężenia pierwiastków znacznikowych w trakcie odlewania stali. Na podstawie otrzymanych danych uzyskano charakterystyki opisujące strefę przejściową.

EN

The article presents an analysis of hydrodynamic conditions and the transient mixing zone for industrial "delta "-shaped tundish. To evaluate conditions of transient mixing zone forming ezamination for the change of marker elements concentration during steel casting was performed. On the basis of results charakteris tics describing the transient zone have been obtained.