Dynamic Modelling and Model Predictive Control of a Continuous Pulp Digester

This work explores the model predictive controller design of the continuous pulp digester process consisting of the co-current zone and counter-current zone modelled by a set of nonlinear coupled hyperbolic partial differential equations (PDE). The distributed parameter system of interest is not spectral and slow-fast dynamic separation does not hold. To address this challenge, the nonlinear continuous-time model is linearized and discretized in time utilizing the Cayley-Tustin discretization framework, which ensures system theoretic properties and structure preservation without spatial discretization or model reduction. The discrete model is used in the full state model predictive controller design, which is augmented by the Luenberger observer design to achieve the output constrained regulation. Finally, a numerical example is provided to demonstrate the feasibility and applicability of the proposed controller designs.

PECULIARITIES OF FLOW AND MIXTURE FORMATION IN MICROIET BURNER DEVICES WITH ASYMMETRIC FUEL DISTRIBUTION

The purpose of the work is to establish the regularities of the isothermal flow and the mixture formation of the fuel gas and oxidant in the microjet burner devices with an asymmetric fuel supply. The main tasks of the work are the analysis of the effects of the influence of the value of excess air factor on the flow structure and the features of the mixing of fuel and oxidant. As a method of research, the CFD modeling method using the FLUENT code was used. According to the results of the studies carried out in the relatively wide limits of the change in the excess air factor (1.5 ≤ α ≤ 4.0), the regularities of the effect of the value of this factor on such flow characteristics in the burners studied as the length of the reverse current zone behind the flame stabilizer, which is responsible for the combustion stability, the location of main vortex in this zone, the values of the mean-square velocity pulsations, and so on. The features of the mixture formation in the variation of the α value in the burner devices under investigation are revealed. The dependence on the mean α of the methane concentration in the reciprocal zone is established and given its interpretation, taking into account a number of competing factors.

Modeling and Analysis of Zone-Based Registration in Mobile Communication Network by Considering Busy-Line Effect and Implicit Registration

In this study, we consider zone-based registration (ZBR) in mobile communication networks. In ZBR, when a mobile moves to a new zone, it registers its zone to the network database to keep the mobile’s current zone, and to connect an incoming call to the mobile when it is generated. A mobile can store one zone, or more than one zones. Among various types of ZBR, we focus on two-zone-based registration (TZR), which is known to have good performance. In TZR, a mobile can store two zones that it has recently registered, and does not register when it crosses either zone that it has already kept. In general, in TZR, a mobile registers its zone less often than in single-zone-based registration (SZR). However, TZR increases the paging cost, because the network may not know the exact zone where the mobile is. Mathematical modeling and performance analysis are performed to obtain the exact performance of SZR and TZR, by considering the busy-line effect and implicit registration effect of outgoing calls from a mobile. From numerical results for various circumstances, it is shown that TZR is superior to SZR in most cases.

Internal Waves Impact on the Sea Surface

The impact of subsurface currents induced by internal waves on nonlinear Stokes surface waves is theoretically analyzed. An analytical and numerical solution of the modulation equations are found under the conditions close to the group velocity resonance. It is shown that smoothing of the down current surface waves is accompanied by a relatively high-frequency modulation while the profile of the opposing current is reproduced by the surface wave’s envelope. The possibility of generation of an internal wave forerunner, that is a modulated surface wavepacket, is established. Long surface waves can form the wave modulation forerunner ahead of the internal wave, while the relatively short surface waves create the trace of the internal wave. Modulation of surface waves by the periodic internal wave train may have the characteristic period less than the internal wave period and be no uniform while crossing the current zone. Surface wave excitation by internal waves, observable at their group resonance is efficient only on the opposing current.

Exposure of internal waves on the sea surface

We theoretically analyse the impact of subsurface currents induced by internal waves on nonlinear Stokes surface waves. We present analytical and numerical solutions of the modulation equations under conditions that are close to group velocity resonance. Our results show that smoothing of the downcurrent surface waves is accompanied by a relatively high-frequency modulation, while the profile of the opposing current is reproduced by the surface wave's envelope. We confirm the possibility of generating an internal wave forerunner that is a modulated surface wave packet. Long surface waves can create such a wave modulation forerunner ahead of the internal wave, while other relatively short surface waves comprise the trace of the internal wave itself. Modulation of surface waves by a periodic internal wavetrain may exhibit a characteristic period that is less than the internal wave period. This period can be non-uniform while the wave crosses the current zone. Our results confirm that surface wave excitation by means of internal waves, as observed at their group resonance frequencies, is efficient only in the context of opposing currents.

Effect of Activated Sludge Processes on Secondary Settling Tank Efficiencies

Some calculations and experimental work on the turbulence in aeration tanks using different aeration systems and its effect on floc cohesion are presented. Vigorous aeration causes floc dispersion and it can be quantified in standard test conditions using velocity gradient calculations and comparing these with the numbers of particles in the supernatant liquor after 30 minutes settlement of the sludge. Tests on final settlement tanks indicated that the density current is of prime importance and that the harmful effects of this can be overcome by installing deep inlets and arranging to have the outlet weir inset and as near to the inlet as possible. Mixing calculations also indicated that circular tanks are more efficient than rectangular and that if the latter were used transverse flow is better than longitudinal flow. A test on a full scale plant indicated that flocculation occurred in the density current zone of the final tank so that the number of particles in the supernatant decreased to an extent similar to that produced by mild agitation.