Inferring Unobserved Events in Systems with Shared Resources and Queues

To identify the causes of performance problems or to predict process behavior, it is essential to have correct and complete event data. This is particularly important for distributed systems with shared resources, e.g., one case can block another case competing for the same machine, leading to inter-case dependencies in performance. However, due to a variety of reasons, real-life systems often record only a subset of all events taking place. To understand and analyze the behavior and performance of processes with shared resources, we aim to reconstruct bounds for timestamps of events in a case that must have happened but were not recorded by inference over events in other cases in the system. We formulate and solve the problem by systematically introducing multi-entity concepts in event logs and process models. We introduce a partial-order based model of a multi-entity event log and a corresponding compositional model for multi-entity processes. We define PQR-systems as a special class of multi-entity processes with shared resources and queues. We then study the problem of inferring from an incomplete event log unobserved events and their timestamps that are globally consistent with a PQR-system. We solve the problem by reconstructing unobserved traces of resources and queues according to the PQR-model and derive bounds for their timestamps using a linear program. While the problem is illustrated for material handling systems like baggage handling systems in airports, the approach can be applied to other settings where recording is incomplete. The ideas have been implemented in ProM and were evaluated using both synthetic and real-life event logs.

New Insights from Locally Resolved Hydrodynamics in Stirred Cell Culture Reactors

The link between hydrodynamics and biological process behavior of antibody-producing mammalian cell cultures is still not fully understood. Common methods to describe dependencies refer mostly to averaged hydrodynamic parameters obtained for individual cultivation systems. In this study, cellular effects and locally resolved hydrodynamics were investigated for impellers with different spatial hydrodynamics. Therefore, the hydrodynamics, mainly flow velocity, shear rate and power input, in a single- and a three-impeller bioreactor setup were analyzed by means of CFD simulations, and cultivation experiments with antibody-producing Chinese hamster ovary (CHO) cells were performed at various agitation rates in both reactor setups. Within the three-impeller bioreactor setup, cells could be cultivated successfully at much higher agitation rates as in the single-impeller bioreactor, probably due to a more uniform flow pattern. It could be shown that this different behavior cannot be linked to parameters commonly used to describe shear effects on cells such as the mean energy dissipation rate or the Kolmogorov length scale, even if this concept is extended by locally resolved hydrodynamic parameters. Alternatively, the hydrodynamic heterogeneity was statistically quantified by means of variance coefficients of the hydrodynamic parameters fluid velocity, shear rate, and energy dissipation rate. The calculated variance coefficients of all hydrodynamic parameters were higher in the setup with three impellers than in the single impeller setup, which might explain the rather stable process behavior in multiple impeller systems due to the reduced hydrodynamic heterogeneity. Such comprehensive insights lead to a deeper understanding of the bioprocess.

Numerical Simulation of Fluid Flow and Mixing Dynamics inside Planetary Roller Extruders

In this contribution, the fluid flow and mixing dynamics inside planetary roller extruders are simulated using the finite element method (FEM) and the mesh superposition technique (MST). Three-dimensional configurations with planetary spindles of varying number and geometry of planetary spindles were created to analyse the influence of the spindle configuration and the rotational speed on the process behavior. Therefore, pressure gradients, flow velocities and directions, shear rates, the mixing index and residence time distributions were evaluated. The distributive and dispersive mixing efficiencies varied depending on the planetary spindle configuration, and these configurations thus suit different processing tasks. In comparison to the standard planetary spindles, the TT3 spindles, with their incomplete toothing, and the knob spindles, with their double transversal helical toothing, showed intense axial and radial mixing. In general, the mixing performance of the planetary roller extruder is explained by a high rate of extensional flow and frequent changes in flow type. The reported numerical approach allows, for the first time, a comprehensive observation of the process behavior of planetary roller extruders.

Process Behavior of Short Glass Fiber Filled Systems during Powder Bed Fusion and Its Effect on Part Dimensions

In powder bed fusion of polymers, filled systems can provide a wide range of part properties, which is still a deficit in additive manufacturing, as the material variety is limited. Glass fiber filled polymers provide a higher strength and stiffness in parts; nevertheless, the process behavior differs from neat polymer systems. In this study, the optical properties and their effect on the part dimensions are analyzed. A higher glass fiber content leads to an increased absorption of laser energy, while the specific heat capacity decreases. This results in larger part dimensions due to higher energy input into the powder bed. The aim of the study is to gain process understanding in terms of ongoing mechanisms during processing filled systems on the one hand and to derive strategies for filled polymer systems in powder bed fusion on the other hand.

Theoretical Description for Omeprazole Cathodical Electrochemical Determination, Assisted by Omeprazole Electrochemical Determination, Assisted by the Composite Poly(1,2,4-triazole) – VO(OH)

In this work, we describe theoretically the possibility of omeprazole electrochemical determination, assisted by the composite containing vanadium oxyhydroxide as an active substance and the polymer of 1,2,4-triazolic derivative as a mediator. The omeprazole molecule undergoes a sulfoxide to sulfide reduction process over a trivalent vanadium compound. The vanadium oxyhydroxide, at its turn, may be oxidized to a tetravalent state, represented in two forms. The electroanalytical process behavior will be illustrated by a trivariate equation-set, analysis of which confirms the efficiency of the composite of poly (1,2,4-triazole) with VO(OH). Vanadium (III) oxyhydroxide may be efficiently used for omeprazole detection both in pharmaceutical formulations, food, and biological liquids.

Optimization and Estimation of Transfer Function Model of Milk Evaporation Process

Development of Mathematical model has significant role in many applications such as estimation of relations between input and output variables. The relations can be deterministic or behavioral. From the point of view of control actions to be estimated for a particular application, behavioral model is considered to be of utmost importance. This also amounts the prediction of process behavior in time, frequency and complex domains. Here in this paper, attempts have been made to develop behavioral model of milk evaporation used in dairy industry which is of prominent importance in India because of its agriculture based economy. Besides India, there are also many milk producing countries in the world and their economy is dependent on milk producing animals. It is also imperative that excess milk production to be converted in its preservable form and evaporated milk has special significance in this context. The Milk evaporation is a complex process and its output control variables depend on many of its input manipulation variables. Because of its complex nature and many variables involved in it poses a challenge real life MIMO problem. In this paper, MIMO model of Milk evaporation model is estimated and described.

Nucleation of SiO$$_{2}$$-CaO-Al$$_{2}$$O$$_{3}$$ Slag in Oxidative Ladle Refining of Metallurgical Grade Silicon

Oxidative ladle refining (OLR) is the most used refining method in industrial production of metallurgical grade silicon. OLR is performed by purging the liquid alloy with oxygen-enhanced air at 1823 K to 1873 K, reacting with silicon and the primary slag forming impurities to a SiO$$_{2}$$ 2 -CaO-Al$$_{2}$$ 2 O$$_{3}$$ 3 slag. To further increase our capability to control this process, it is paramount to understand how the slag nucleates and forms, and represent it such that it is useful for predicting and controlling the process behavior. This work aims to formulate a comprehensive theoretical description of slag nucleation and formation at nano/microscale using classical macroscale thermodynamics, bridging these spatial regimes. To achieve this, the work argues that silica’s liquid structure allows its nuclei to exhibit “well defined” surfaces. Furthermore, silica is predicted to be highly surface active, so if its concentration is high while the slag nucleus is small, the SiO$$_{2}$$ 2 -CaO-Al$$_{2}$$ 2 O$$_{3}$$ 3 slag should retain silica’s surface properties. An experiment confirmed the surface active nature of silica in the SiO$$_{2}$$ 2 -CaO-Al$$_{2}$$ 2 O$$_{3}$$ 3 system. It was also shown that increasing the slag’s calcia concentration has a greater effect on the interfacial tension between the molten slag and liquid alloy than alumina, confirming industrial observations of the coupling between refining rate and relative alloy/slag composition.