Spectroscopic models for real-time monitoring of cell culture processes using spatiotemporal just-in-time Gaussian processes

Spectroscopic methods play an instrumental role in the implementation of the U.S. Food and Drug Administration outlined process analytical technology for biopharmaceutical manufacturing. Industrial spectroscopic calibration models are typically developed in an offline setting using traditional methods, such as partial least squares and principal component regression. Apart from the limiting performances of these conventional models under time-varying operating conditions, these methods require access to extensive historical data, which are seldom available in biopharmaceutical manufacturing. In this article, we propose a novel spatiotemporal just-in-time learning (ST-JITL) based spectroscopic model calibration platform for automatic training and maintenance of calibration models using routine batch data. The proposed ST-JITL framework uses Gaussian processes (GPs) for local model calibration. A GP model not only exhibits superior performance over traditional methods but also provides credibility intervals around the model predictions. The efficacy of the ST-JITL based model calibration platform is demonstrated in predicting the critical performance parameters of an industrial cell culture process.     

Novel 0D/1D ZnBi2O4/ZnO S-scheme photocatalyst for hydrogen production and BPA removal

Developing interfacial connections is one of the breakthrough strategies to improve the photocatalytic activity. Herein, ZnBi₂O₄ nanoparticles-ZnO nanorods heterojunction was successfully synthesized and used, as a dual-function photocatalyst, for photocatalytic degradation of Bisphenol A and hydrogen production with improved photocatalytic activity under simulated sunlight irradiation. The highest H₂ production (3.44 mmol g^?1 h^?1) was obtained for ZnO-20 wt% ZnBi₂O₄ sample, which is around 12.7 times higher than pure ZnO. According to the HRTEM result, the intimate interfacial connections are formed between ZnO and ZnBi₂O₄ which could act as trapping centers for charge carriers and results in the boosted photocatalytic activity. Further, a high aspect ratio of 1D ZnO nanorods and small size of 0D ZnBi₂O₄ nanoparticles (~10 nm) increases the number of interfacial contacts and thus the charge carriers’ recombination was suppressed more efficiently. Based on the trapping experiments, ESR and Mott-Schottky analysis, ZnBi₂O₄–ZnO hybrid photocatalyst followed the S-scheme charge transfer mechanism.     

Comparative study of heat transfer and pressure drop for curved-twisted tubes utilized in chemical engineering

Increasing importance of heat transfer in chemical engineering science causes that investigation in the field of enhancement techniques is always one of the up-to-date topics for study. In the current comparative analysis, the thermal enhancement and friction penalty are explored numerically for curved tubes via twisted configuration. To accomplish this, three common geometries namely helical, serpentine, and Archimedes spiral, are considered at different coil-pitches and twist-pitches as well as five Reynolds numbers in the laminar flow regime. The results exhibit noticeable enhancements (up to 60%) in the thermal performance of the twisted cases as compared to the smooth cases. The highest increases are recorded for the serpentine case, followed by the helical and spiral cases. It is found that these enhancements vary via coil-pitch and twist-pitch. Increasing coil-pitch and twist-pitch augments both heat transfer coefficient and pressure drop in all curved-twisted tubes, however, the effects of twist-pitch are more pronounced. To predict Nusselt number and friction factor, new correlations are also proposed. The maximum deviations of the predicted results compared to the simulated data are within ±5%.     

Effect of thermal stresses on stability and frequency response of a capacitive microphone

This article deals with effects of thermal stresses on stability and frequency response of a fully clamped circular microplate, which acts as the diaphragm of a capacitive MEMS microphone. Static and dynamic pull-in phenomena limit the stable regions of a capacitive MEMS microphone. The results show that the non-dimensional static pull-in voltage of the studied case is about 5.23 (38.6 V). On the other hand, according to the results, the non-dimensional dynamic pull-in of the diaphragm is about 4.74 (34.98 V), which is as low as 90.63% of the static pull-in threshold. Because of the thermal expansion coefficient, diaphragm temperature increment leads to compressive thermal stresses and conversely, decrement of the diaphragm temperature creates tensile thermal stresses. The effect of temperature on the pull-in parameters is given by a design-correcting factor.As results demonstrate, the deflection of the diaphragm subjected to a given electrostatic force can be controlled by means of the temperature changes. In the absence of electrostatic force, as the results show, although temperature changes do not create any deflection, but for a critical temperature increment the diaphragm stiffness vanishes and the buckling phenomenon takes place. Effects of the electrostatic force and the temperature variation on the frequency response of the microphone subjected to a sound pressure wave are investigated. As the results illustrate, increment of the electrostatic force or increment of the diaphragm temperature increases the output level and sensitivity of the microphone and decreases the fundamental frequency of the microphone, limiting the upper band of its bandwidth. It is obvious that decrement of the diaphragm temperature acts conversely. In addition, the results show that in the presence of the electrostatic force sensitivity of the output level of the diaphragm to the temperature change increases.     

A dynamic replicator model of the players’ bids in an oligopolistic electricity market

In this paper, the replicator dynamics of the power suppliers’ bids in an oligopolistic electricity market are derived for both the fixed and variable demand cases. The replicator dynamics stability analysis is also performed. The dynamics of the electricity markets are the results of players’ decisions. The physical parameters of the power systems (such as the lines capacities, voltage limitations, etc.) also affect the market dynamics indirectly, through the changes in players’ behaviors. Assuming rational players, an optimal bidding strategy for constructing the supply function (SF) of a generating firm is presented and based on that, the dynamics of the bid replicators are studied. Both fixed demands and price sensitive demands are taken into account. The replicator model is presented in the well-known state space structure. A case study is presented to show the applicability of the developed dynamic replicator bid model, and also to show how the Nash–SFE equilibrium evolves over time.     

Project time–cost trade-off scheduling: a hybrid optimization approach

This paper develops a hybrid approach for stochastic time–cost trade-off problem (STCTP) in PERT networks of project management, where activities are subjected to linear cost functions. The main objective of proposed approach is to improve the project completion probability in a prespecified deadline from a risky value to a confident predefined probability. To this end, we construct a nonlinear mathematical program with decision variables of activity mean durations, in which the objective function is concerned with minimization of project crashing direct cost. In order to solve the constructed model, we present a hybrid approach based on cutting plane method and Monte Carlo (MC) simulation. To illustrate the process of proposed approach, the approach was coded using MATLAB 7.6.0 and two illustrative examples are discussed. The results obtained from the computational study show that the proposed algorithm is an effective approach for the STCTP.     

An efficient formulation for thin-walled beams curved in plan

An efficient formulation is developed for the elastic analysis of thin-walled beams curved in plan. Using a second-order rotation tensor, the strain values of the deformed configuration are calculated in terms of the displacement values and the initial curvature by adopting the right extensional strain measure. The principle of virtual work is then used to obtain the nonlinear equilibrium equations, based on which a finite element beam formulation is developed. The accuracy of the method is confirmed through comparison with test results, shell finite element formulations and other curved beam formulations from the literature. It is also shown that the results of the developed formulation are very accurate for the cases where initial curvature is large.     

Influence of Wall Material and Inlet Drying Air Temperature on the Microencapsulation of Fish Oil by Spray Drying

Several single and composite milk-originated wall materials were used to microencapsulate fish oil via spray drying at various inlet drying air temperatures. Skim milk powder (SMP), whey protein concentrate, whey protein isolate (WPI), 80% WPI?+?20% milk protein concentrate, and 80% WPI?+?20% sodium caseinate (NaCas) were applied as the wall for capsules generated at drying air temperatures of 140, 160, and 180 °C. The higher the drying air temperature, the higher was the particle size, encapsulation efficiency, and peroxide value and the lower was the moisture content and bulk density. The microcapsules prepared with SMP showed the highest encapsulation efficiency and lowest peroxide value for the oil due to the presence of lactose in its chemical composition. Differential scanning calorimetry and Fourier transform infrared analyses indicated the absence of any significant interaction between SMP and fish oil.