Simulation of liquid phase accumulation at centrifugal dewatering of activated sludge

Centrifugation of activated sludge is a frequently used dewatering process but there is a need for a fitting function for moderate and high sludge concentrations. In particular, liquid phase accumulation kinetics during centrifugation may be used as a source of information about sedimentation properties and governing mechanism of the cake formation. This will allow the obtention of the optimal parameters for the dewatering control and process optimisation. For this purpose, activated sludge at different concentrations was investigated on a laboratory centrifuge with centrifugation factor 2667. The following sludges were used in the experiments: 1) activated sludge from thickener (with and without floculant treatment); 2) sludge after industrial centrifuge decanter Flottweg Z62-4 collected from dumping pound; sludge (2) after anaerobic treatment; sludge (2) with a dispersed solid additive. Based on the obtained data, the following assumption was made: settling of the solid phase and cake compaction depends on the hindered settling velocity and sediment compression. Due to the applied centrifuge force, a primary cake skeleton from particular aggregates and flocs is formed. During this stage, free water is displaced from the space between aggregates/flocs with a further transition to the compaction of the sediment with the water being displaced from the pores of the flocs by a filtration mechanism until an equilibrium condition is reached. The liquid volume V vs. time t at hindered settling and sediment dewatering can be represented in the form Vα tⁿ, where n ≤1.0. Therefore, in log-log coordinates, the kinetics of liquid accumulation have a linear dependence lg(V ) α n lg(t) in both settling and compaction stages. This assumption was confirmed for different types of activated sludge. Using asymptotical analysis in the function form F(t,V) , a dimensionless fitting function was obtained that describes the centrifugation of activated sludge. For highly concentrated sludge, it was found that the dewatering occurs as cake compression. Analysis of deformation models leads to the conclusion that for the compressible cake it is necessary to introduce a parameter characterising the cake plasticity dependence on the centrifugation time. Developed model was used for fitting numerous experimental data. The main advantage of proposed model is the possibility to fit the liquid phase accumulation kinetics during centrifugation in a wide range of the activated sludge concentration, from suspension up to structured and paste-like cake consistency. The extension of this model to other slurries requires further investigation

Pairing of applicants’ CJM with university profile in digital environment as a management task

The work is devoted to the application of the Customer Journey Map (CJM) for university applicants and managerial tasks of adapting the profile of the university in the digital environment to the trajectories of the consumer. The author’s definition of the “profile of the university in the digital environment” concept is offered, the analysis of statistical data of university websites is made. The combination of classical studies of applicants’ motivation and factors influencing enrollment in a particular university with modern methods of studying consumer behavior in the digital environment allows to increase the effectiveness of the admission campaign. Customer Journey Map as an analysis tool, in conjunction with the data of network traffic allows to optimize all types of communications of the university and provide its management with necessary information when making managerial decisions. The research revealed an insignificant influence of the university social networks and thematic groups on the decision to enroll to a particular university, which what caused a deeper study of visitors’ behavior on the university websites. Internet traffic activity for a number of universities was assessed as direct requests, through search services, social networks, mail servers, as well as through referral links, and advertising traffic. The study showed that search engines and direct queries gave the maximum value for traffic. But the effectiveness of advertising to attract applicants is rather low, which indicates the insignificant role of university advertising and confirms the data of the survey in the construction of the Customer Journey Map

Detailed comparison of the pp -> \pi^+pn and pp -> \pi^+d reactions at 951 MeV

The positively charged pions produced in proton-proton collisions at a beam momentum of 1640 MeV/c were measured in the forward direction with a high resolution magnetic spectrograph. The missing mass distribution shows the bound state (deuteron) clearly separated from the $pn$ continuum. Despite the very good resolution, there is no evidence for any significant production of the $pn$ system in the spin-singlet state. However, the $\sigma(pp\to \pi^+pn)/\sigma(pp\to \pi^+d)$ cross section ratio is about twice as large as that predicted from $S$-wave final-state-interaction theory and it is suggested that this is due to $D$-state effects in the $pn$ system.Comment: 8 pages, 3 figure

Delta isobar masses, large N_c relations, and the quark model

Motivated by recent remarks on the Delta+ mass and comparisons between the quark model and relations based on large-N_c with perturbative flavor breaking, two sets of Delta masses consistent with these constraints are constructed. These two sets, based either on an experimentally determined mass splitting or a quark model of isospin symmetry breaking, are shown to be inconsistent. The model dependence of this inconsistency is examined, and suggestions for improved experiments are made. An explicit quark model calculation and mass relations based on the large-N_c limit with perturbative flavor breaking are compared. The expected level of accuracy of such relations is realized in the quark model, except for mass relations spanning more than one SU(6) representation. It is shown that the Delta0 and Delta++ pole masses and Delta0 - Delta+ = (Delta- - Delta++)/3 about 1.5 MeV are more consistent with model expectations than the analogous Breit-Wigner masses and their splittings.Comment: 10 pages, including 1 eps figure, revte

Production of the 1S0 diproton in the pp -> pp pi0 reaction at 0.8 GeV

The pp -> pp pi0 differential cross section has been measured with the ANKE spectrometer at COSY-Juelich for pion cms angles between 0 and 15.4 degrees at a proton beam energy of 0.8 GeV. The selection of diproton pairs with an excitation energy E_{pp} < 3 MeV ensures that the final pp system is dominantly in the spin-singlet 1S0 state. The kinematics are therefore very similar to those of pp -> d pi+ but with different spin and isospin transitions. The results will thus provide a crucial extra test of pion production models in nucleon-nucleon collisions. The cross sections, which are over two orders of magnitude smaller than those of pp -> d pi+, show a forward dip, even stronger than that seen at lower energies. This behaviour is well reproduced in a theoretical model that includes P-wave Delta-N states.Comment: 10 pages, 5 eps figures, prepared using elsart.cl

Forward K+ production in subthreshold pA collisions at 1.0 GeV

K+ meson production in pA (A = C, Cu, Au) collisions has been studied using the ANKE spectrometer at an internal target position of the COSY-Juelich accelerator. The complete momentum spectrum of kaons emitted at forward angles, theta < 12 degrees, has been measured for a beam energy of T(p)=1.0 GeV, far below the free NN threshold of 1.58 GeV. The spectrum does not follow a thermal distribution at low kaon momenta and the larger momenta reflect a high degree of collectivity in the target nucleus.Comment: 4 pages, 3 figure

Decuplet contribution to the meson-baryon scattering lengths

We calculate decuplet contributions to the s-wave pseudoscalar meson octet-baryon scattering lengths to the third order in heavy baryon chiral perturbation theory (HB$\chi$PT). Using experimental pion-nucleon and kaon-nucleon scattering lengths as inputs, we determine low-energy constants and predict other meson-baryon scattering lengths. Numerically we consider three cases: (1) the case with only baryon octet contributions; (2) with decuplet contributions and (3) in the large $N_c$ limit. Hopefully, the analytical expressions and the predictions are helpful to future investigations of the meson-baryon scattering lengths

Dependence of calculated binding energies and widths of η\eta-mesic nuclei on treatment of subthreshold η\eta-nucleon interaction

We demonstrate that the binding energies and widths of eta-mesic nuclei depend strongly on subthreshold eta-N interaction. This strong dependence is made evident from comparing three different eta-nucleus optical potentials: (1) a microscopic optical potential taking into account the full effects of off-shell eta-nucleon interactions; (2) a factorization approximation to the microscopic optical potential where a downward energy shift parameter is introduced to approximate the subthreshold eta-nucleon interaction; and (3) an optical potential using on-shell eta-nucleon scattering length as the interaction input. Our analysis indicates that the in-medium $\eta$N interaction for bound-state formation is about 30 MeV below the free-space $\eta$N threshold, which causes a substantial reduction of the attractive force between the $\eta$ and nucleon with respect to that implied by the scattering length. Consequently, the scattering-length approach overpredicts the binding energies and caution must be exercised when these latter predictions are used as guide in searching for $\eta$-nucleus bound states. We also show that final-state-interaction analysis cannot provide an unequivocal determination of the existence of $\eta$-nucleus bound state. More direct measurements are, therefore, necessary.Comment: 28 pages, 1 figur

Eta-N Final State Interaction in incoherent Photoproduction of Eta-mesons from the Deuteron near Threshold

An analysis of incoherent photoproduction of $\eta$ mesons off the deuteron for photon energies from threshold to 800 MeV is presented. The dominant contribution, the $\gamma$N-$\eta$N amplitude, is described within an isobar model. Effects of the final state interactions in the $NN$ as well as the ${\eta}N$ systems are included employing models derived within the meson-exchange approach. It is found that their consideration is important. Specifically, due to an interference effect the influence of the $\eta N$ final state interaction is enhanced in the reaction $\gamma d \to np \eta$ close to threshold.Comment: 11 pages (LaTeX), 7 postscript figure

Comparative constructions of similarity in Northern Samoyedic languages

The purpose of this paper is to analyze the suffixes which are used in Northern Samoyedic languages to build comparative constructions of equality. Depending on the language, the suffixes may perform three functions: word-building, form-building, and inflectional. When they mark the noun, they serve as simulative suffixes and are employed to build object comparison. In the inflectional function, these suffixes mark the verb and are a means of constructing situational comparison. In this case, they signal the formation of a special mood termed the Approximative. This paper provides a detailed description of the Approximative from paradigmatic and syntagmatic perspectives