Circular Flow Research Articles

Electrocatalytic Hydrogenation of Pyridines and Other Nitrogen-Containing Aromatic Compounds.

The production of cyclic amines, which are vital to the pharmaceutical industry, relies on energy-intensive thermochemical hydrogenation. Herein, we demonstrate the electrocatalytic hydrogenation of nitrogen-containing aromatic compounds, specifically pyridine, at ambient temperature and pressure via a membrane electrode assembly with an anion-exchange membrane. We synthesized piperidine using a carbon-supported rhodium catalyst, achieving a current density of 25 mA cm-2 and a current efficiency of 99% under a circular flow until 5 F mol-1. Quantitative conversion of pyridine into piperidine with 98% yield was observed after passing 9 F mol-1, corresponding to 65% of current efficiency. The reduction of Rh oxides on the catalyst surface was crucial for catalysis. The Rh(0) surface interacts moderately with piperidine, decreasing the energy required for the rate-determining desorption step. The proposed process is applicable to other nitrogen-containing aromatic compounds and could be efficiently scaled up. This method presents clear advantages over traditional high-temperature and high-pressure thermochemical catalytic processes.

Assessment methods and digital tools to support circular building strategies

Abstract The aim of the paper is to highlight how digital technology can be a vector for maintaining information of buildings products, promoting supply chain transparency and traceability of materials and environmental data, contributing to activate a sustainable circular economy. Indeed, the current lack of knowledge of product characteristics often hinders the activation of reverse logistic and the assessment of the environmental benefits of circular material flows. This means, on one hand, the need to trace and collect product characteristics and product environmental information throughout the entire life cycle, and, on the other hand, the to identify ways of communicating and sharing information. This paper outlines current digital tools to support transparency and traceability of materials. Next, the paper verticalises the method and indicators used to declare the circular and sustainable profile of products, emphasising the importance of applying Life Cycle Assessment (LCA). Finally, the prefiguration of a possible integration between traceability tools and the LCA methodology is discussed, identifying possible drivers (e.g. legislative, trainings) and possible key-operators for the widespread of the “LCA-integrated traceability tools”.

Concentric circular flow field to improve mass transport in large-scale proton exchange membrane water electrolysis cells

Uniform reactant supply is challenging for high-performance proton exchange membrane water electrolysis (PEMWE) in renewable energy storage. The anode flow-field pattern, anode flow-field orientation, and stoichiometric ratio influence mass transport. In this study, the performances of two flow-field patterns were compared for a single PEMWE cell with an active area of 100 cm2. Straight serpentine was used as the reference model and a concentric circle with an arc shape was designed. In addition, the optimal anode flow field orientation and stoichiometric ratio were determined. The results indicate that the optimal anode flow-field pattern differs depending on the stoichiometric ratio. At low flow rates, mass transfer via diffusion was dominant; therefore, a straight serpentine flow was preferred. In contrast, a concentric circle, which induces a significant differential pressure between adjacent channels, is preferable at a high flow rate. This is because convection is dominant in mass transfer. Maintaining a stoichiometric ratio of 10 or more is recommended during the operation. At a ratio of less than 10, the reactant was depleted at a high current density, and the mass transfer resistance increased. In addition, water is better distributed by gravity and buoyancy when the electrolyte membrane is parallel to the ground, and the anode flow path is above the porous medium. This leads to high PEMWE cell performance.

Fabrication Information Modeling for Closed-Loop Design and Quality Improvement in Additive Manufacturing for construction

Additive Manufacturing (AM) has emerged as a disruptive technology with the potential to revolutionize the construction industry by integrating digital design with automated manufacturing. This paper presents and extends Fabrication Information Modeling (FIM), a comprehensive framework tailored for automated manufacturing in construction. FIM facilitates the seamless integration of digital design concepts with automated manufacturing processes, enabling precise control over fabrication information and enhancing construction efficiency and quality. This paper demonstrates its potential to optimize construction processes through a detailed exploration of FIM’s capabilities, including data preparation, path planning, simulation integration, robot control, and data feedback. By enabling a circular data flow between digital modeling and manufacturing, FIM is able to bridge the gap between digital design and physical construction, revolutionizing how construction projects are conceived, planned, and executed. The paper concludes by highlighting the challenges and future research directions in advancing FIM-based construction systems, emphasizing its transformative potential in driving innovation and sustainability in the construction industry.

Remittance Inflow, Investment, and Economic Growth in Africa amidst COVID-19 Pandemic

Africa has fared well in the aspect of remittance receipts in recent years; however, the region recorded a decline in remittances amid the COVID-19 pandemic which constrained the circular flow of income significantly and ultimately economic growth. In view of this, this study investigates the economic effects of remittance inflows and investment on economic growth in Africa amid COVID-19 pandemic using a panel of 48 economies and estimated with pooled OLS and two-step system GMM. The study employed two distinct approaches for estimation; pre-COVID-19 (2010–2019) and amid COVID-19 (2010–2023). The results indicate that the behavior of remittances, investment and economic growth in Africa is not significantly different between pre-COVID-19 and amid COVID-19. That is, remittances remain a significant economic growth catalyst in Africa whereas investment is not (though with growth effect potential). Overall, the study concludes that African economic policy stakeholders and other relevant policy authorities should sustain the current remittance and labor policy frameworks with possible fine-tuning where applicable while doubling their investment efforts especially in productive sectors of the economy.

Trajectory and spreading of falling circular dense jets in shallow stagnant ambient water

This study investigates the trajectory and spreading of a horizontal circular dense jet flow discharged above the water surface, the flow of which falls into shallow stagnant ambient water. For this purpose, 27 experiments were performed using three diameters, flow rates, and falling heights to investigate jet trajectory. In addition, nine experiments with constant falling height were conducted to study jet spreading. The densimetric Froude number of the jet flow at the nozzle outlet and water surface of the present study ranged from 0.72 to 4.22 and 36.96 to 86.10, respectively. The data pertaining to this study were extracted and analyzed through image processing. The results of the experiments showed that by increasing both the momentum and falling height, the trajectory of the jet flow reached a farther distance from the discharge nozzle. The spreading of the outer boundaries of the dense circular falling jet flow tended to extend downstream of the impact point and had an elliptical motion on the bed. The relationship between radial distance from the impingement point to the outer boundary of flow and time was determined to have a power of 0.67 for flow along the flume and 0.59 for flow along the flume's width.

Testing Algorithms for Controlling the Distributed Power Supply System of a Railway Signal Box

Trends in the use of renewable energy sources to power buildings do not bypass objects for which maintaining a power supply is critical. This also applies to railway signal boxes. The aim of the research work was to test the multisource power supply system for a railway signal box with power electronic converter systems and a DC bus, built as part of the research project. The assumption for powering the railway signal box building was to use renewable sources, energy storage devices, and a 3 kV DC traction network as the second required power supply grid. Both power grids were connected by power electronic converters, and the power values of the converters were set based on the calculated power balance values using the values measured at the system nodes and the set constraints. The tests primarily tested the response of the power supply system to changes in load power and power generated by the photovoltaic source, as well as the charge level of the energy storage devices. The correctness of the control algorithm’s operation was assessed based on the recorded power values in the power supply system nodes. The tests were carried out for 60 scenarios that covered all normal and emergency operating conditions. During the tests, delays in response to changes in the power supplied to the converters and the values of circular power flow between the power grid connections were recorded. The recorded delays ranged from 2 to about 50 s and the circular power flows did not exceed 1500 W. Based on the results of the tests, it was found necessary to improve the power measurement system in the power supply system nodes and to improve the quality of communication and the transmission time of measurement data transmission time.

Maximally efficient exchange in thin flow cells using density gradients

Flow cells are ubiquitous in laboratories and automated instrumentation, and are crucial for ease of sample preparation, analyte addition and buffer exchange. The assumption that the fluids have exchanged completely in a flow cell is often critical to data interpretation. This article describes the buoyancy effects on the exchange of fluids with differing densities or viscosities in thin, circular flow cells. Depending on the flow direction, fluid exchange varies from highly efficient to drastically incomplete, even after a large excess of exchange volume. Numerical solutions to the Navier–Stokes and Cahn–Hilliard equations match well with experimental observations. This leads to quantitative predictions of the conditions where buoyancy forces in thin flow cells are significant. A novel method is introduced for exchanging fluid cells by accounting for and utilizing buoyancy effects that can be essential to obtain accurate results from measurements performed within closed-volume fluid environments.

A novel compartmental approach for modeling stomach motility and gastric emptying

The stomach, a central organ in the Gastrointestinal (GI) tract, regulates the processing of ingested food through gastric motility and emptying. Understanding the stomach function is crucial for treating gastric disorders. Experimental studies in this field often face difficulties due to limitations and invasiveness of available techniques and ethical concerns. To counter this, researchers resort to computational and numerical methods. However, existing computational studies often isolate one aspect of the stomach function while neglecting the rest and employ computationally expensive methods. This paper proposes a novel cost-efficient multi-compartmental model, offering a comprehensive insight into gastric function at an organ level, thus presenting a promising alternative.The proposed approach divides the spatial geometry of the stomach into four compartments: Proximal/Middle/Terminal antrum and Pyloric sphincter. Each compartment is characterized by a set of ordinary differential equations (ODEs) with respect to time to characterize the stomach function. Electrophysiology is represented by simplified equations reflecting the “slow wave behavior” of Interstitial Cells of Cajal (ICC) and Smooth Muscle Cells (SMC) in the stomach wall. An electro-mechanical coupling model translates SMC “slow waves” into smooth muscle contractions. Muscle contractions induce peristalsis, affecting gastric fluid flow velocity and subsequent emptying when the pyloric sphincter is open. Contraction of the pyloric sphincter initiates a retrograde flow jet at the terminal antrum, modeled by a circular liquid jet flow equation.The results from the proposed model for a healthy human stomach were compared with experimental and computational studies on electrophysiology, muscle tissue mechanics, and fluid behavior during gastric emptying. These findings revealed that each “ICC” slow wave corresponded to a muscle contraction due to electro-mechanical coupling behavior. The rate of gastric emptying and mixing efficiency decreased with increasing viscosity of gastric liquid but remained relatively unchanged with gastric liquid density variations. Utilizing different ODE solvers in MATLAB, the model was solved, with ode15s demonstrating the fastest computation time, simulating 180 s of real-time stomach response in just 2.7 s. This multi-compartmental model signifies a promising advancement in understanding gastric function, providing a cost-effective and comprehensive approach to study complex interactions within the stomach and test innovative therapies like neuromodulation for treating gastric disorders.

Freecycling Markets as Sustainable Materialist Movements?

This paper seeks to redress the over-emphasis on state-driven circular policies in public and academic discourses by attending to two physical community-based freecycling markets at the emerging frontiers of circular waste/resource management in Singapore. Freecycling markets that close short reuse loops are a counterpoint to policies that close long recycling loops. Drawing primarily on empirical data from ethnographic fieldwork, we argue that freecycling markets exemplify a sustainable materialist movement concerned about the sustainability of material resources vis-à-vis the closing/shortening of material circularity loops. This is achieved through the reconfiguration of (a) material flows and (b) material relations. The redirection of unwanted but reusable household objects away from the incinerator and towards potential reusers animates a shift from a linear to circular material flow. We contend that this redirection of material resources for reuse is augmented by rescue and recirculation, which are relatively neglected within the scholarship on circular R-behaviours. Additionally, freecycling markets seek to transform material relations by encouraging care and stewardship, instead of use and disposal. Crucially, we highlight how freecycling markets may be plagued with material constraints that render them not-so-sustainable-and-scalable, thereby shedding light on the practical limits of sustainable materialist action. Taken together, this paper extends the scholarship on circular economies by bringing work on sustainable materialism into a productive dialogue with that on circular activisms and R-behaviours.

Income circular flow and its impact on sustainable agricultural productivity

Income circular flow and its impact on sustainable agricultural productivity

Syndrome differentiation treatment and nursing of hydrocele basing on the theory of the circular flow of Qi

Syndrome differentiation treatment and nursing of hydrocele basing on the theory of the circular flow of Qi

Use of innovative sample dryer for effective sample drying in forensic investigations: An experimental study

Back groundThe sample collection and preservation before transportation to a Forensic Science Laboratory in a medicolegal case in India is a crucial step in establishing a link between accused, victim, crime scene and the weapon. This paper discusses pioneering advancement in health technology—a state-of-the-art sample dryer developed to preserve biological samples during Forensic investigations. This unique design has been officially registered with the design office in India as a copy right. Aims and ObjectivesThe primary goal of the sample dryer is to augment the preservation of biological evidence by removing moisture content through air drying before packaging, sealing and its transportation to a Forensic Science Laboratory. Material and MethodsThe process of air drying of biological samples by variety of experiments conducted in sample’s dryer designed for the purpose which employs a range of air movement techniques including horizontal, vertical, and circular laminar flows to swiftly extract moisture from the samples. The drying duration for each experimental sample was documented upon manual confirmation of complete drying. ResultsThe results were extraordinary, showcasing that the sample’s dryer reduced the drying time drastically by up to 27 times lesser in comparison to conventional methods for identical samples. The diverse airflow patterns generated by the sample dryer unequivocally demonstrated it’s utility in achieving superior sample preservation through efficient air drying. ConclusionGiven the exceptional outcomes observed in the experimental phase, the authors strongly advocate for the widespread adoption of this innovative sample’s dryer equipment to ensure effective air drying of biological samples and their efficient sample preservation to enable successful forensic analysis as expected.

Environmental multipliers for circular flow–positive-profit economies: formulation, implications and empirical illustration

Environmental multipliers for circular flow–positive-profit economies: formulation, implications and empirical illustration

The reversed circular flow jet impingement (RCFJI) PV/T collector: Thermohydraulic and electrohydraulic analysis

AbstractSolar energy could be used to generate both electricity and heat with the aid of photovoltaic thermal (PV/T) systems. Although the systems have a variety of advantages, they nevertheless hold a significant constraint. The system suffers a susceptible constraint wherein the photovoltaic (PV) module experiences an increase in temperature due to exposure to solar irradiation. The integration of a cooling system is necessary to enhance its operational efficiency. A novel approach, known as the reversed circular flow jet impingement (RCFJI), was proposed as a means to improve the performance of a PV/T collector. The current work seeks to assess the thermohydraulic and electrohydraulic performance of the RCFJI PV/T collector. The experiment was conducted under an irradiance level of 500–900 W/m2. From the result obtained, the thermohydraulic efficiency reached its maximum value of 59.20% under 900 W/m2 at 0.14 kg/s. Conversely, the electrohydraulic efficiency attained the highest reading of 10.91% under 500 W/m2 at 0.13 kg/s. It was concluded that a higher flow rate reduces the friction coefficient while increasing the pressure drop. The thermohydraulic and electrohydraulic analyses emphasize the importance of assessing the friction coefficient and pressure drop to attain optimal performance. This study addresses the lack of research by presenting a new cooling approach that utilizes jet impingement. In addition, this study provides an understanding of the thermohydraulic and electrohydraulic performance of a RCFJI PV/T collector.

How digital platforms can be leveraged to enable closed material loops – An example of the steel supply chain

Increasing demands for limited natural resources accelerate rethinking their usage and processing. A focal point of interest lies in the steel industry, given its substantial contribution to emissions and the notable attribute of steel being fully recyclable. Hence, closing material loops to ensure the preservation of material value and supply security is of substantial importance. Yet, until today, supply chains are still characterized by interrupted information streams that prevent circular material flows. Digital platforms are attributed to overcoming these shortcomings due to their ability to moderate ecosystems and render technological connectivity. However, industrial companies lack knowledge of how digital platforms can be used to design closed material loops. Therefore, this paper is built on a longitudinal case study of a joint venture between a recycling and steel melting plant company aiming at creating a digital platform to close the material flow of steel. Six design priorities, structured along the three core building blocks of digital platform ecosystems and the four core dimensions of collective action theory (CAT), have been derived to guide managers in designing digital platforms for the CE-specific context. This study presently contributes to understanding the relationship between digital platforms and CE.

Towards Time-Resolved Multi-Property Measurements By Single-Frequency FRS

The filtered Rayleigh scattering technique (FRS), extended by the method of frequency scanning, has historically been limited to time-averaged multi-property flow measurements. In our recently published work, we present a concept that potentially enables the combined measurement of time-resolved pressure, temperature and three-component (3C) velocity fields. It is based on the observation of the region of interest from six perspectives and a single excitation frequency. This work summarizes and expands on a follow-up publication that experimentally verifies this concept on an aspirated circular duct flow. For this purpose, the results obtained from single-frequency data processing are compared with reference pressures, temperatures and corresponding LDA velocity measurements. Overall, a very good agreement is found for all operating points with accuracies of 3.4% in pressure, 1.3% in temperature and ±2 m/s in axial velocity. Concerning precision, a newly developed multistage evaluation procedure enables values for pressure, temperature and velocity as low as 3 hPa, 2.2 K and 1.7 m/s. In a second flow configuration, an axial swirler is introduced into the duct. The resulting secondary flow structure and deformation of the axial velocity field caused by swirler geometry and support are very well captured with the single-frequency analysis. A closing discussion on the implementation challenges of a single-frequency multi-property FRS instrument with pulsed laser radiation reveals significant obstacles to overcome. Due the considerable optimization potential identified, chances are high that true time-resolved multi-property measurements by FRS will become a reality.

Predicting pressure fields from incomplete velocity fields based on deep convolutional neural network

Acquisition of an instantaneous pressure field in a flow field is essential for experimental fluid dynamics research because pressure is associated with various flow phenomena. Machine learning has performed well in various fluid mechanics studies in recent years due to its nonlinearity. In this paper, we use the machine learning method to predict the pressure fields from incomplete velocity fields while reconstructing the missing velocity information, as exemplified by the stationary circular cylinder flow and circular cylinder undergoing forced oscillating problems, in which the incompleteness of the velocity field is caused by the optical path occlusion in experiments. We propose a network model based on convolutional neural networks. The experimental results show that the error of machine learning methods is around 4%, and even if the resolution of the training set is reduced, it does not affect the prediction accuracy of the network. For statistical averaging of prediction results, the network has high accuracy in predicting first-order quantities, but its ability to predict second-order quantities is limited. We also explore the effects of the amount of noise on the performance of networks. When applying the model to the forced oscillating cylinder problem, we use transfer learning to train the network given the similarity of the two problems, and the training error yields faster convergence and more minor convergence results. In addition to this, we use flow field data with a single vibration frequency to construct a single dataset, and flow field data with multiple vibration frequencies to construct a mixed dataset, and study the effect of different datasets on the prediction accuracy, which shows that it is difficult for neural networks to achieve both accuracy and generalization.

High-Lift Aerodynamics of Integrated Distributed Propulsion Systems with Thrust Vectoring

Recent interest in distributed electric propulsion in aeronautics has motivated the exploration of novel approaches for integrating this technology into fixed-wing aircraft. Quasi-two-dimensional wind tunnel experiments were conducted with an aeropropulsive airfoil model, which included 10 integrated electric ducted fans and trailing-edge thrust vectoring capability. The experimental model was designed based on a reference aeropropulsive system originally optimized for transonic flight conditions. The model incorporated flow conditioners to separate the capture streamtubes of each fan and transition the circular internal flow into a rectangular nozzle exit. The system angle of attack, thrust coefficient, and nozzle deflection angle were all varied throughout the study. Surface pressure data, aggregate lift, drag, and pitching moment performance, and individual fan thrust data were all collected. Experimental results show an increased lift curve slope and maximum lift coefficient with larger fan thrust alongside larger aerodynamic contributions to drag and pitching moment. Deflection of hinged flaps to vector thrust reduces the airfoil zero-lift and stall angles of attack, similar to traditional trailing-edge flaps. Finally, thrust-drag bookkeeping methods demonstrate how jet momentum and airfoil aerodynamics interact. This experiment intends to highlight the aerodynamic mechanisms through which integrated propulsors couple with airfoils to achieve high-lift performance.

Control of light-induced torque in quantum well waveguides through electron spin coherence

We explore the mechanical effects of light interacting with a quantum well waveguide, specifically focusing on the emergence of quantized torque. We investigate the response of the waveguide to the influence of two intense coupling fields in conjunction with two weaker fields. We find that the electron spin coherence plays a crucial role in amplifying the torque applied to the waveguide emitters. This heightened torque, in turn, triggers a distinctive circular current flow pattern within the waveguide. Furthermore, we explore different scenarios for modulating the torque by adjusting system parameters, thereby establishing a means to control current flow. The emergence of a light-induced quantized torque not only illuminates the interplay between quantum emitters and electromagnetic fields but also opens up exciting possibilities for innovative approaches to govern induced-torque behavior within quantum well waveguides.