Cyclic Operation Research Articles

Pressure-Driven Batch Distillation Optimal Control for Ethanol-Water Separation

Ethanol-water separation by pressure-swing batch distillation in a double-batch rectifier system is a process under investigation. In this work, a complete global solution to the optimal control problem in the form of a sequential synthesis of controlled trajectories is derived. During this study, the optimal reflux strategy through cyclic operation was extended to the separation of a second non-ideal minimum boiling azeotrope of industrial importance. The optimal cyclic reflux ratio operating policy, brought significant reductions in time duration, going up to even 50%. Consequently even more significant reductions in energy expenditure, since the derived discontinuous energy function tends to show cyclic “behavior” as well. Lastly, the proposed strategy provides the possibility to highly recover the desired product even within a single period, and finally maybe even the most importantly, flexibility in operating different units within the time frame.

A Modified Decentralized Droop Control Method to Eliminate Battery Short-Term Operation in a Hybrid Supercapacitor/Battery Energy Storage System

Employment of a battery energy storage system to compensate for the generation-consumption mismatch is a vital element for a resilient microgrid. However, the frequent (i.e., short-term) cyclic activity and the abrupt current variations (i.e., high di/dt) have adverse effects on the energy-type battery’s lifespan. On the other hand, the power-type supercapacitor energy storage system (SCES) has almost zero lifetime degradation when it is subjected to irregular charging/discharging patterns. Therefore, the hybridization between them can reduce battery stress levels. This study proposes a droop control algorithm with multiple segments for a SCES/battery hybrid energy storage system (HESS) that is employed in a solar/wind DC microgrid. The presented control scheme is decentralized since it avoids the central controller (CC) and the communication links between the controllers of SCES and battery units. To eliminate the short-term cyclic operation of the battery, the SCES regulates the bus voltage inside a narrow zone with a droop curve that exploits all its available energy capacity. Inside this zone, the battery is kept inactive. As soon as the bus voltage deviates from this band, the SCES enters the idle mode, and the battery is triggered following a droop curve different for charging or discharging mode to stabilize the bus voltage. To evaluate the effectiveness of the proposed system over a battery-only system and a hybrid SCES/battery system controlled with the classical droop method, a comparative analysis under different scenarios is presented.

Thermo-mechanical fatigue induced unexpected strain hardening of Cu clip wiring on transfer-mold type EV power modules

Power modules subjected to cyclic power operation experience thermomechanical fatigue. Herein, the epoxy molding compounds and creep behaviors of solder joints promoted the strain hardening of the Cu clip wiring and caused failure to the power module during the power operations. In the Cu clips, the grain size was refined by 90% from the failure stage compared to the initial state, and an increase in hardness was observed. The results indicate that constraints of EMC and the creep behaviors of solder joints are other critical factors for the role of bare Cu clip strain hardening of EV power modules.

Use of scanning electron microscopy and energy dispersive X-ray spectroscopy to identify key fouling species during alternating tangential filtration.

Alternating tangential flow filtration (ATF) has become one of the primary methods for cell retention and clarification in perfusion bioreactors. However, membrane fouling can cause product sieving losses that limit the performance of these systems. This study used scanning electron microscopy and energy dispersive X-ray spectroscopy to identify the nature and location of foulants on 0.2μm polyethersulfone hollow fiber membranes after use in industrial Chinese hamster ovary cell perfusion bioreactors for monoclonal antibody production. Membrane fouling was dominated by proteinaceous material, primarily host cell proteins along with some monoclonal antibody. Fouling occurred primarily on the lumen surface with much less protein trapped within the depth of the fiber. Protein deposition was also most pronounced near the inlet/exit of the hollow fibers, which are the regions with the greatest flux (and transmembrane pressure) during the cyclical operation of the ATF. These results provide important insights into the underlying phenomena governing the fouling behavior of ATF systems for continuous bioprocessing.

An improved Closed-Circuit RO (CCRO) system: Design and cyclic simulation

A volume-varying stirred tank with a free-piston are placed in front of DuPont's Closed-Circuit RO (CCRO) system to achieve improved energetics. Valves are used to direct fluid flow and piston motion to enable cyclic operations consisting of CC filtration and flushing steps. Similar to CCRO, overall system recovery in the proposed system is controlled by the CC/flushing time ratio, and uninterrupted permeate production is possible if the flushing is done at high pressures. Spatiotemporal system-level models are developed and formulated as a set of coupled partial differential equations (PDEs) and ordinary differential equations (ODEs). Detailed numerical simulations and parametric studies are carried out to explore the flow and mass transfer characteristics and to compare its performance at the cyclic steady-state (CSS) with the original CCRO and the conventional steady-state RO.

Centres, trace functors, and cyclic cohomology

We study the biclosedness of the monoidal categories of modules and comodules over a (left or right) Hopf algebroid, along with their bimodule category centres over the respective opposite categories and a corresponding categorical equivalence to anti Yetter-Drinfel’d contramodules and anti Yetter-Drinfel’d modules, respectively. This is directly connected to the existence of a trace functor on the monoidal categories of modules and comodules in question, which in turn allows to recover (or define) cyclic operators enabling cyclic cohomology.

Comparative study of models for packed bed molten salt storage systems

To date various models for packed bed single tank molten salt storage systems have been developed. The question arises in how far certain modelling assumptions can affect the outcome of these models. This can also depend on the applied use case, for example a short validation simulation versus an annual simulation. Thus, a comparative study is performed, considering four one-dimensional models for packed beds: the Schumann model, the continuous-solid-phase model, the single-phase model and a recently developed bidisperse model. Additionally, the impact of heat losses and variable fluid properties are considered as well. The comparison is performed for different use cases and covers the single blow operation, cyclic operation and annual simulations. Common boundary conditions are derived from a 100 MWel concentrating solar thermal power plant with molten salt as heat transfer fluid. A large and a small storage volume, each with a small and a large particle packing are designed to cover a range of practical storage configurations. The aim of this work is to provide guidelines for the selection of a reasonable level of modelling detail depending on the desired accuracy and computational effort. Results indicate that the outcome can significantly differ between the use cases. Effective conductivity has visible impact in stand-by periods and small sized packings with strong thermal gradients. The single-phase model has low computing effort but is applicable only with packings in the range of millimeters. The bidisperse model has significantly improved accuracy when applied to packings with smaller particles in combination with larger particles. Heat losses showed little impact for the considered storage volumes. Temperature dependent fluid properties have an impact within short periods but average out in cyclic and annual simulations, which justifies neglecting them.

Cellulase production from disposed COVID-19 personal protective equipment (PPE) using cyclic fed-batch strategies

Wild fungal strain-employing, cellulase production bio-processes require 17-fold higher quantities of lignocelluloses than biofuel production. Globally-available, conventional lignocelluloses are 3 × 103-fold lesser than their requirement for bio-alcohol-fossil fuel blending purposes. In an attempt to explore biomass alternatives, demonstrate their potential in cellulase production, and to simultaneously-address process-deterring conditions of solid-state and submerged fermentations, cellulose-rich, COVID-19 personal protective equipment-based substrates were used in time-extended, empirical data-driven, optimal condition-maintaining cyclic fed-batch strategies. While 37% and 43% increases of cumulative cellulase yields were recorded for solid and submerged cyclic operations, respectively, they were 21% and 28% more economical than multiple, individual batches. Furthermore, the operations improved kinetics of fungal growth, oxygen transfer, nutrient utilization, and maintained optimal parameter balance between variables, thereby improving consistency in cellulase titers. Apart from being sustainable, the demonstration suggests a recycle route for managing such health hazard-posing wastes, in turn alleviating environmental pollution and earning carbon credits.

Simulation-based framework for optimal construction equipment allocation considering construction noise emissions

ABSTRACT As construction noise has been a major environmental emission from the construction sites, construction equipment allocation should be planned to preemptively manage construction noise emissions while considering productivity. Therefore, this study aims to propose a simulation-based framework for determining optimal construction equipment allocation to manage construction noise and improve economic performance. The optimal construction equipment allocation in terms of direct cost and noise exposure was determined using a Web-based CYCLic Operation NEtwork (WebCYCLONE) and exhaustive search technique. The feasibility of the proposed framework was validated through a case study of a real project. The proposed framework could predict direct costs and noise emissions of the construction process within the allowable error. Based on the simulation-based prediction, the optimal allocation in terms of direct cost and noise exposure level reduces USD 2,186.65 (24.6%) out of USD 8,873.84 in the direct cost or 4.4 dB (5.0%) out of 88.59 dB in noise exposure level of residents. Moreover, the optimal allocation in terms of direct cost and compensation cost reduces USD 881.45 (0.6%) out of USD 154,316.63 in the overall costs. Finally, the proposed framework could help construction managers establish a plan to improve the economic and environmental performances in the planning stage.

Ultrahigh cyclic stability and giant elastocaloric effect in directionally solidified (Ni50Mn28Fe2.5Ti19.5)99.4B0.6 alloy

Cyclic stability of elastocaloric materials is critically important for practical applications in solid-state refrigeration. Ni-Mn-based Heusler-type alloys exhibit a large elastocaloric response to low driving stress. However, these alloys can only be worked for short-term cyclic operation due to their intrinsic brittleness. Here, we demonstrate the achievement of giant elastocaloric effect (eCE) and long-term fatigue performance in a directional solidification (Ni50Mn28Fe2.5Ti19.5)99.4B0.6 alloy. At 303 K, the maximum compressive strength and strain of the alloy can be as high as 2734 MPa and 20.5%, respectively. During fast loading and unloading with the stress of 435 MPa and the strain of 8%, giant adiabatic temperature change (ΔTad) of 25.1 K and -24.5 K can be obtained, respectively. In particular, a large ΔTad of about 5.8 K is generated during cycling at 360 MPa stress and 3.5% strain, and can be maintained for more than 20,000 cycles.

The Use of Correlation Features in the Problem of Speech Recognition

The problem solved in the article is connected with the increase in the efficiency of phraseological radio exchange message recognition, which sometimes takes place in conditions of increased tension for the pilot. For high-quality recognition, signal preprocessing methods are needed. The article considers new data preprocessing algorithms used to extract features from a speech message. In this case, two approaches were proposed. The first approach is building autocorrelation functions of messages based on the Fourier transform, the second one uses the idea of building autocorrelation portraits of speech signals. The proposed approaches are quite simple to implement, although they require cyclic operators, since they work with pairs of samples from the original signal. Approbation of the developed method was carried out with the problem of recognizing phraseological radio exchange messages in Russian. The algorithm with preliminary feature extraction provides a gain of 1.7% in recognition accuracy. The use of convolutional neural networks also provides an increase in recognition efficiency. The gain for autocorrelation portraits processing is about 3–4%. Quantization is used to optimize the proposed models. The algorithm’s performance increased by 2.8 times after the quantization. It was also possible to increase accuracy of recognition by 1–2% using digital signal processing algorithms. An important feature of the proposed algorithms is the possibility of generalizing them to arbitrary data with time correlation. The speech message preprocessing algorithms discussed in this article are based on classical digital signal processing algorithms. The idea of constructing autocorrelation portraits based on the time series of a signal has a novelty. At the same time, this approach ensures high recognition accuracy. However, the study also showed that all the algorithms under consideration perform quite poorly under the influence of strong noise.

Measurement of Water Vapor Condensation on Apple Surfaces during Controlled Atmosphere Storage.

Apples are stored at temperatures close to 0 °C and high relative humidity (up to 95%) under controlled atmosphere conditions. Under these conditions, the cyclic operation of the refrigeration machine and the associated temperature fluctuations can lead to localized undershoots of the dew point on fruit surfaces. The primary question for the present study was to prove that such condensation processes can be measured under practical conditions during apple storage. Using the example of a measuring point in the upper apple layer of a large bin in the supply air area, this evidence was provided. Using two independent measuring methods, a wetness sensor attached to the apple surface and determination of climatic conditions near the fruit, the phases of condensation, namely active condensation and evaporation, were measured over three weeks as a function of the operating time of the cooling system components (refrigeration machine, fans, defrosting regime). The system for measurement and continuous data acquisition in the case of an airtight CA-storage room is presented and the influence of the operation of the cooling system components in relation to condensation phenomena was evaluated. Depending on the set point specifications for ventilation and defrost control, condensed water was present on the apple surface between 33.4% and 100% of the duration of the varying cooling/re-warming cycles.

Single‐Step Oxidation of Low‐Concentration Methane to Methanol in the Gaseous Phase Using Ceria‐Based Iridium‐Copper Catalysts

AbstractSingle‐step conversion of methane to methanol in the gaseous phase is required for high value added application of methane and environmental protection, but it is challenging. Here, direct oxidation of methane to methanol under gaseous condition on iridium promoted Cu/CeO2 catalyst, prepared using a sol‐gel method, is investigated. The addition of iridium can effectively upgrade the redox properties and oxygen storage capacity due to intense metal interaction, stimulating a prominent catalytic performance for methane conversion to methanol on Cu−Ir@CeO2 catalyst. Approximately 26.2 μmol/gcat methanol yield and 68 % methanol selectivity are achieved on the trimetallic 5Cu0.5Ir@CeO2 catalyst at 550 °C in 2 h. Consequences of the analysis of XRD, SEM, HRTEM, Raman, FI‐IR and XPS demonstrate that highly‐dispersed Ir and Cu species are uniformly distributed on CeO2 surface, and partial Cu or Ir atoms replace Ce4+ in CeO2 lattice due to the metal interaction in the colloidal structure, which can impact the catalyst's electronic properties. H2 temperature‐programmed reduction (H2‐TPR) and CH4 temperature‐programmed desorption (CH4‐TPD) results disclose that the unique ternary surface exhibits excellent redox properties and strong adsorption capacity for methane, which can activate the first C−H bond of methane to methyl species, and then react with OH− to form methanol. The good stability in cyclic operation is an additional attribute, rendering this type of catalyst a “front‐runner” in future catalyst development for direct methane‐to‐methanol. This composite catalyst design provides hope for developing ternary metal‐oxide catalysts for functionalization of methane.

Fourth-order tensor calculus operations and application to continuum mechanics

This paper provides a presentation of differential calculus involving fourth-order tensors in consideration of the cyclic class-based tensor operations introduced in an earlier paper on fourth-order tensor algebraic operations. Three classes of cyclic second-order tensor operators, denoted by dot, cross, and star, with separate definitions for double contraction, quadruple contraction, and tensor products were recognized. The present paper examines the differentiation of second-order isotropic tensor functions with respect to a second-order tensor, taking into account the three classes of second-order tensor operators. Product rules, chain rules, and identities necessary to maintain consistency are defined. In combining the proposed calculus rules with the second-order tensor operators, a comprehensive set of proofs for the power derivatives is first presented. A closed-form solution for the second-order tensor derivative of an isotropic tensor function is also detailed. Some of the new solutions are an outcome of capabilities offered by new operators and identities provided in the literature. The paper is arranged so as to be a useful reference work with regard to the mathematics of fourth-order tensors in absolute notation, particularly for application in the field of continuum mechanics in engineering.

A Novel Miniature and Selective CMOS Gas Sensor for Gas Mixture Analysis-Part 3: Extending the Chemical Modeling.

This is the third part of the paper presenting a miniature, combustion-type gas sensor (dubbed GMOS) based on a novel thermal sensor (dubbed TMOS). The TMOS is a micromachined CMOS-SOI transistor, which acts as the sensing element and is integrated with a catalytic reaction plate, where ignition of the gas takes place. The first part was focused on the chemical and technological aspects of the sensor. In Part 2, the emphasis was on the physical aspects of the reaction micro-hot plate on which the catalytic layer is deposited. The present study focuses on applying several advanced simulation tools, which extend our understanding of the GMOS performance, as well as pellistor sensors in general. The three main challenges in simulating the performance are: (i) how to define the operating temperature based on the input parameters; (ii) how to measure the dynamics of the temperature increase during cyclic operation at a given duty cycle; (iii) how to model the correlation between the operating temperature and the sensing response. The simulated and analytical models and measured results are shown to be in good agreement.

Bang-Bang control of active and reactive powers in photovoltaic power plants for transient stability improvement and oscillation damping

This paper utilizes the fast response capability of the photovoltaic power plants (PVPPs) in providing active and reactive power to increase transient stability margin and oscillation damping in the power system along with improving energy conversion efficiency. The new half cyclic operation (HCO) method is based on the Bang-Bang control of active and reactive power in PVPPs, which does not need any power curtailment. While oscillation is detected, the control system starts to sequentially half-cyclic switch the control system between stability mode and maximum power point tracking (MPPT) mode. Switching between MPPT and stability modes helps with energy conversion efficiency increment, rotor oscillation damping, and transient stability improvement. This strategy automatically leads the operation point to MPPT as oscillation gets mitigated. IEEE 9-bus and IEEE 39-bus test systems are used for representing new control method performances. The obtained results prove the effectiveness of the proposed strategy.

Humidity‐Driven High‐Performance Electrothermal Actuation of Vertically Stacked 2D PtTe2 Layers/Cellulose Nanofibers

A new type of soft actuators based on a vertical stack of nanoporous 2,2,6,6‐tetramethylpiperidine‐1‐oxyl‐oxidized cellulose nanofibers (TOCNs) and atomically thin 2D platinum ditelluride (PtTe2) layers is reported. The actuation of TOCNs is driven by the interfacing 2D PtTe2 layers whose electrothermal proficiency precisely controls their hydration/dehydration states sensitive to mechanical deformation. These vertically stacked TOCN/2D PtTe2 actuators present excellent actuation characteristics such as high linearity of bending curvature versus applied voltage and well‐preserved reversibility during cyclic operations. Most notably, they exhibit an extremely large weight‐lifting ratio, i.e., ≈1000 times the mass of the TOCN layers, confirming superior mechanical robustness. Furthermore, complicated actuations such as twisting in a 3D manner are demonstrated by judiciously controlling the surface wettability of TOCN layers. This study unveils opportunities for CNFs and 2D materials for actuator applications, as well as suggests new design strategies broadly applicable to soft robotics and biomimetic devices.

Sorption enhanced steam reforming of ethanol for hydrogen production, over Mg/Al hydrotalcites modified with K

Sorption-enhanced ethanol steam reforming is an interesting alternative, to produce high purity H2. In this study, potassium promoted hydrotalcites are compared for sorption-enhanced ethanol steam reforming reaction under cyclic operation, performing sorbent regeneration at reaction temperature which is a great advantage to reduce process energy requirements. It is found that potassium promoted hydrotalcites have higher CO2 sorption capacity compared to unpromoted ones, due to the higher concentration of intermediate and strong basic sites. The hydrotalcite modified with 15 wt% potassium shows the best performance on multicyclic CO2 sorption-desorption (sorption capacity = 0.167 molCO2/kgsorbent). Therefore, there is an optimum loading of potassium, for which the opposite effects of reduction in surface area and enhanced basicity are balanced. Finally, potassium promoted hydrotalcites are tested under cyclical ethanol reforming process with simultaneous adsorption of CO2 followed by regeneration in N2 at reaction temperature (500 °C). At short reaction times (<5 min), H2 purities higher than 95% are achieved, with CO2 purities near 0%.

Measurement of shrinkage void and identification of solid-liquid phases in phase change materials: Ultrasound-based approach and simulated predictions

Phase change materials in thermal energy storage systems undergo solidification and melting during cyclic operations. During solidification, internal shrinkage voids are formed randomly in phase change materials due to density differences in the solid and liquid phases. These shrinkage voids can severely affect the heat transfer performance and storage capacity of thermal energy storage systems. Additionally, the containers in which phase change materials are kept are usually metallic, making them opaque. Therefore, identification of the solid–liquid phase by direct visualisation during the phase change is limited. The present work aims to develop a non-destructive ultrasonic scanning approach to detect and measure internal shrinkage voids in solid phase change materials and the solid–liquid phases during melting and perform multi-phase numerical simulations that simultaneously capture solidification/melting and the associated shrinkage/expansion. The most commonly used phase change materials, n-eicosane, and n-octadecane, are used in this study. The effectiveness of the ultrasonic technique is evaluated by measuring cavities of known sizes. Further, three cases are considered for examining and measuring the shrinkage void. Case A involves two-dimensional solidification with a surface void, while Case B and C involve three-dimensional solidification with an internal shrinkage void. The numerically obtained shrinkage cavity profile shows a maximum deviation of 7.8% with experimental results for case C. Furthermore, the developed approach is implemented to uniquely detect and identify the solid and liquid phases during melting in an opaque container.

Fouling and Mitigation Behavior of Foulants on Ion Exchange Membranes with Surface Property in Reverse Electrodialysis.

In this study, two different types of ion exchange membranes are used to investigate the tendency of membrane fouling with respect to surface roughness and hydrophilicity. Commercially available membranes reinforced by electrospun nanofiber have rough and hydrophilic surfaces, and lab-made pore-filling membranes exhibit a smooth and hydrophobic surface. Three different organic surfactants (i.e., cationic, anionic and non-ionic surfactants) are chosen as foulants with similar molecular weights. It is confirmed that membrane fouling by electrical attraction mainly occurs, in which anionic and cationic foulants influence anion and cation exchange membranes, respectively. Thus, less fouling is obtained on both membranes for the non-charged foulant. The membranes with a rough surface show a higher fouling tendency than those with a smooth surface in the short-term continuous fouling tests. However, during the cyclic operations of fouling and mitigation of the commercially available membranes, the irregularities of a rough membrane surface cause a rapid increase in electrical resistance from the beginning of fouling due to excessive adsorption on the surface, but the fouling is easily mitigated due to the hydrophilic surface. On the other hand, the membranes with a smooth surface show alleviated fouling from the beginning of fouling, but the irreversible fouling occurs as foulants accumulate on the hydrophobic surface which causes membrane fouling to be favorable.