Exchange Process Research Articles

Water Injection for Cloud Cavitation Suppression: Analysis of the Effects of Injection Parameters

This study investigates cloud cavitation suppression around a model-scale NACA66 hydrofoil using active water injection and explores the effect of multiple injection parameters. Numerical simulations and a mixed-level orthogonal test method are employed to systematically analyze the impact of jet angle αjet, jet location Ljet, and jet velocity Ujet on cavitation suppression efficiency and hydrofoil energy performance. The study reveals that jet location has the greatest influence on cavitation suppression, while jet angle has the greatest influence on hydrofoil energy performance. The optimal parameter combination (Ljet = 0.30C, αjet = +60 degrees, Ujet = 3.25 m/s) effectively balances energy performance and cavitation suppression, reducing cavitation volume by 49.34% and improving lift–drag ratio by 8.55%. The study found that the jet’s introduction not only enhances vapor condensation and reduces the intensity of the vapor–liquid exchange process but also disrupts the internal structure of cavitation clouds and elevates pressure on the hydrofoil suction surface, thereby effectively suppressing cavitation. Further analysis shows that positive-going horizontal jet components enhance the lift–drag ratio, while negative-going components have a detrimental effect. Jet arrangements near the trailing edge negatively impact both cavitation suppression and energy performance. These findings provide a valuable reference for selecting optimal injection parameters to achieve a balance between cavitation suppression and energy performance in hydrodynamic systems.

A Computer Laboratory for the Calculation of the Heat Capacity of a Peptide Unfolding Transition

ABSTRACT We present the implementation of a computer simulation laboratory for the calculation of the heat capacity of the folding-unfolding pseudo phase transition of a polyalanine Ala30 α-helix, using molecular dynamics simulations. Unlike conventional calorimetry experiments, which provide a macroscopic interpretation of the heat capacity, the computer laboratory additionally offers a molecular perspective of the energy exchange processes that lead to the peak of the heat capacity at the phase transition, as well as the statistical mechanical interpretation of the phase transition. The exercise is targeted toward 1st- or 2nd-year students of biophysics in the context of an undergraduate physical chemistry course. We use a graphical web interface to overcome the steep learning barriers associated with command line interactions in commonly used molecular dynamics protocols. The web interface (VIKING) also handles communication with computing hardware in the background, so that students with limited or no programming experience can launch and analyze the simulations easily. A collaboration between the VIKING support team and responsible teachers is required to set up VIKING. We also present a solution in which simulations can be launched on students’ own computers, if some command line knowledge can be expected. The laboratory can also be repurposed for students of various backgrounds (physics, chemistry, biology, or engineering) and scholastic levels (undergraduate or graduate).

Using Networks to Engage Community Health Workers in Participatory Action Research in High-Poverty Rural Communities

Previous research shows that health and social service networks can improve service and system coordination and increase capacity to respond to critical social determinants and health needs. This article describes strategies, methods and tools used to engage community health workers (CHWs) in the development and implementation of initiatives associated with the COVID-19 Response Network, a collaborative between academicians, regional clinical and social service administrators, practitioners, and regional community and faith-based organizations. Network initiatives included community-based participatory action (CBPT) research approaches to respond to social determinants and health needs in rural Missouri during the COVID-19 pandemic. Mixed methods were used to ascertain the impact of these approaches, including surveys and key informant interviews with Network members. Survey responses showed the network to be a venue where decision-making was democratic, CHW voices were valued, and network members trusted each other. Analysis revealed two themes: How the Network improved CHWs’ capacity to respond to the COVID-19 pandemic (“Getting a seat at the table”) and how trust is built through relational exchange processes (“They need to believe in you”). The results clarify practical approaches to participatory action research for bringing together and maximizing the contributions of a combination of CHWs, clinicians, and administrators in clinical and social services stakeholders in the community in leadership positions to improve health outcomes. Implications for academic researchers and academic institutions are discussed.

Numerical Study of the Influence of Regenerator Structure on the Performance of Hot Blast Stoves

The properties and arrangement of checker bricks in regenerators are crucial for the heat exchange process of hot blast stoves. In this study, a 3D fluid flow heat transfer model is established to analyze the influence of three regenerator layered structures on the combustion and air supply performance of hot blast stoves. The results show that a “silica bricks–high-alumina bricks–clay bricks” three-layer arrangement in regenerators produces a “thermal conduction hindrance effect” at the interface between silica and high-alumina bricks during the 2 h combustion period, which raises the local temperature and improves air supply performance. Compared to the “silica bricks–clay bricks” and “high-alumina bricks–silica bricks–clay bricks” structures, this setup increases the maximum air supply temperature difference to 23 and 64 K, respectively, and extends the effective air supply time by 80 and 320 s, respectively. However, the “thermal conduction hindrance effect” diminishes over longer combustion periods, and by 4 h, the performance across all structures becomes increasingly consistent. Additionally, the study suggests that the temperature level and distribution in the upper part of the regenerator are the key factors determining the air supply performance of hot blast stoves.

Carnelian Beads from the Early Bronze Age Fifa Cemetery, Jordan: Aspects of Technology, Use, and Exchange

Between 1989 and 1990 the Expedition to the Dead Sea Plain excavated a group of 15 tombs at the Early Bronze Age IA (c.3700–3400) cist-tomb cemetery at Fifa, Jordan. These tombs contained a variety of grave goods including beads made from carnelian. The present study employs morphometric data and microscopic indicators of manufacture and use to explore the relationship between carnelian beads, burial practices, manufacturing processes, and exchange. Manufacturing traces suggest that the beads from Fifa were created through a process of knapping and progressive stages of abrasion. Beads were perforated through pecking on one or two sides. Polish from use was observed on beads throughout the assemblage, suggesting that the beads were worn prior to their deposition, albeit for an unknown period of time. The amount of this use polish was highly variable suggesting that different beads were in use for greater or lesser periods of time. Morphometric and manufacturing data were utilized in tandem in order to suggest where the beads were produced. While a great deal of prior scholarship has suggested that carnelian beads found in the Early Bronze Age Levant originated in Egypt, we argue that some or all of these beads may alternatively have been produced in Northwestern Arabia or Eastern Jordan. This study demonstrates the value of systematic approaches to the study of beads in order to better understand processes of ritual behavior, craft production, and exchange.

Time scales and mechanisms of uranium uptake in altered ocean crust; observations from the ∼15 million year-old site 1256 in the eastern equatorial Pacific

The alteration of ocean crust through hydrothermal seawater circulation facilitates chemical exchange between Earth’s surface and interior. Hydrothermal alteration leads to uranium (U) removal from seawater and net U uptake by the ocean crust, particularly during low temperature alteration that occurs on the vast ocean ridge flanks away from the spreading axes. Determining the timescales of U uptake and its associated 238U/235U signature has important implications for understanding U exchange processes during subduction and recycling into the mantle. Here we study the U systematics of ∼15 million year-old ocean crust drilled at Site 1256 on the eastern flank of the East Pacific Rise. Analysis of cores from the upper ∼1300 m of intact ocean crust at this site, reveal large variability in U concentrations and 238U/235U ratios. Many of the samples from the upper ∼600 m of extrusive lavas have elevated U concentrations and 238U/235U ratios lower than seawater, consistent with mechanisms of U uptake under relatively oxidised conditions. Samples from the underlying sheeted dikes and gabbros show evidence for hydrothermal U mobilisation, but negligible net U uptake. In contrast, in the transition zone between the extrusive lavas and the sheeted dikes, samples revealed large U enrichments and high 238U/235U ratios above seawater. This is consistent with uptake of the reduced U+4 species under relatively reducing conditions from seawater-derived hydrothermal fluids. In addition, large secular disequilibrium in 234U/238U ratios from samples in the lava-dike transition and upper sheeted dikes give evidence for U mobility within the last ∼1.5 million years, likely driven by deep channelled flow of seawater-derived hydrothermal fluids combined with preferential leaching of 234U from the rock matrix. Both the total estimated U uptake and mean 238U/235U at Site 1256 is lower than similar estimates from significantly older (>100 million years) altered ocean crusts at drill Sites 801 and 417/418. This shows the variable total U uptake and 238U/235U ratio in altered ocean crust over time, which needs to be taken into consideration when estimating global U budgets.

Knowledge exchange in the arctic environmental studies: Bridging science and the local community in dialogue

In the context of accelerated climate dynamics and uncertainties surrounding climate change research, collaborative approaches to knowledge generation are increasingly cited as a pathway needed for navigating the complexity of challenges. There is a widespread consensus that researcher-community joint expertise deepens our understanding of climatic changes. However, how this unfolds in practical settings lacks rigorous empirical support in the landscape of contemporary environmental studies. The article focuses on the intrinsic process of expert knowledge exchange and creating knowledge-in-action space for meaningful community-researcher partnerships. Addressing these issues draws upon experiences facilitating public events for diverse audiences in different countries and varying settings of scale, format and level of engagement. This account refers to the essential role of dialogue, interactivity, culturally sensitive devotion and visualization as powerful tools in building a platform for knowledge co-creation. It analyzes different ways of designing knowledge exchange that give access to a spectrum of experimentation, self-reflection and liaison with art but also requires mobilizing ethics and flexibility.

Characteristics of thermo‐hydraulic flow inside corrugated channels: Comprehensive and comparative review

AbstractPrevious works that investigated the characteristics of heat transfer and fluid flow in channels with corrugated walls have been extensively reviewed in this study. In accordance with the fast increase in power consumption requirements, many researchers have investigated a new approach for cooling techniques that can enhance the cooling performance of devices without consuming more power. To improve the efficiency of energy systems, many investigators and engineers implement promising techniques such as surface optimization and additives as passive methods to augment the rates of heat transfer. Researchers investigated different corrugation profiles along with various working fluids as well as external power devices to further improve the heat exchange process of thermal systems. The aim of this article is to give a clear preview of the effects of different parameters such as wave parameters, Reynolds number, type of working fluid, and pulsating flow condition on the average and local Nusselt number, the pressure drop, the performance factors, and irreversibility. The main findings are listed in tables and depicted in figures, the matter that helps engineers and researchers to choose a suitable channel shape for their applications.

Multifaceted anchoring ligands for uniform orientation and enhanced cubic-phase stability of perovskite quantum dots

All-inorganic CsPbI3 perovskite quantum dots (PQDs) hold significant potential for next-generation photovoltaics due to their unique optoelectronic properties, and the surface-bound ligand playing a key role in the stability and functionality of CsPbI3 PQDs. Initially used long-chain ligands in PQDs synthesis stabilize the black phase but hinder charge transport when employed to solar cells, necessitating their replacement with shorter ones. However, this leads to the formation of surface defects and loss of tensile strain, resulting in the transition to the undesired orthorhombic phase (δ-phase) and compromising PQD solar cell performance. Therefore, developing a ligand exchange process that achieves the optimal balance between conductivity and stability in PQD solid films continues to be a significant challenge. To address these issues, we developed an efficient ligand-exchange process utilizing a multifaceted anchoring ligand, 2-thiophenemethylammonium iodide (ThMAI). The larger ionic size of ThMA+ compared to Cs+ facilitates the restoration of surface tensile strain in PQDs, while its thiophene and ammonium groups enable effective passivation of surface defects. Owing to these advantages, ThMAI-treated CsPbI3 PQD thin films exhibit improved carrier lifetime, uniform PQD orientation, and increased ambient stability. As a result, the ThMAI-treated CsPbI3 PQD solar cells demonstrate an improved power conversion efficiency (PCE) of 15.3 % and an enhanced device stability.

Insight into Details of Chemical Exchange Kinetics Studied by NMR CPMG Method

A more detailed insight into the chemical kinetics and dynamics of chemical exchanges within a molecule or between molecules in liquids is made possible by the NMR CPMG method, which, in addition to the exchange rate, gives its power spectrum, which contains information about the underlying processes of chemical exchange. The applicability of the method is demonstrated by measuring the chemical exchange in an aqueous solutions of sucrose, whose rate spectra have shapes that cannot be explained as transitions in a double potential well, but after interpretation using the chemical Langevin equations, it can be explained as a cascading chemical transition across several intermediate potential walls.

Molecularly Imprinted Viral Protein Integrated Zn-Cu-In-Se-P Quantum Dots Superlattice for Quantitative Ratiometric Electrochemical Detection of SARS-CoV-2 Spike Protein in Saliva.

Solution-processable colloidal quantum dots (QDs) are promising materials for the development of rapid and low-cost, next-generation quantum-sensing diagnostic systems. In this study, we report on the synthesis of multinary Zn-Cu-In-Se-P (ZCISeP) QDs and the application of the QDs-modified electrode (QDs/SPCE) as a solid superlattice transducer interface for the ratiometric electrochemical detection of the SARS-CoV-2-S1 protein in saliva. The ZCISeP QDs were synthesized through the formation of In(Zn)PSe QDs from InP QDs, followed by the incorporation of Cu cations into the crystal lattice via cation exchange processes. A viral-protein-imprinted polymer film was deposited onto the QDs/SPCE for the specific binding of SARS-CoV-2. Molecular imprinting of the virus protein was achieved using a surface imprinting electropolymerization strategy to create the MIP@QDs/SPCE nanosensor. Characterization through spectroscopic, microscopic, and electrochemical techniques confirmed the structural properties and electronic-band state of the ZCISeP QDs. Cyclic voltammetry studies of the QDs/SPCE superlattice confirmed efficient electron transport properties and revealed an intraband gap energy state with redox peaks attributed to the Cu1+/2+ defects. Binding of SARS-CoV-2-S1 to the MIP@QDs/SPCE cavities induced a gating effect that modulated the Fe(CN)6 3-/4- and Cu1+/2+ redox processes at the nanosensor interface, producing dual off/on ratiometric electrical current signals. Under optimal assay conditions, the nanosensor exhibited a wide linear detection range (0.001-100 pg/mL) and a low detection limit (0.34 pg/mL, 4.6 fM) for quantitative detection of SARS-CoV-2-S1 in saliva. The MIP@QDs/SPCE nanosensor demonstrated excellent selectivity against nonspecific protein targets, and the integration with a smartphone-based potentiostat confirmed the potential for point-of-care applications.

Negotiations on food security at the WTO: a never-ending story?

PurposeThe purpose is to chart the negotiations on the issue of food security which was identified as a non-trade concern by the Agreement on Agriculture (AOA) and how developing Members of the World Trade Organisation (WTO) suggested that that concern should be addressed.Design/methodology/approachThe history of negotiations at the WTO is examined through the lens of official documents submitted during various phases of negotiations since 1996 beginning with the Analysis and Information Exchange process to the Doha Round up to the latest Ministerial Conference in Abu Dhabi in February 2024.FindingsThe negotiations have yet to complete despite beginning over 20 years ago. The focus moved since 2008 to look at specific issues which were addressed at a number of Ministerial Conferences but the latest of these indicate that an answer can only be found in the re-negotiation of the AOA as a whole.Research limitations/implicationsBy focusing on official documents, the rich literature on food security has not been addressed.Practical implicationsThe piece concludes by looking at issues which need to be resolved ahead of agreement on overall reform and suggests solutions for example in the area of safeguards and public stockholding for food security purposes.Originality/valueThe focus almost exclusively on official (and public) documents during the discussion is noteworthy. It also confirms that the WTO is not really that different from its predecessor - the GATT - which took nearly 50 years to reach AOA.

Modeling Ligand Exchange Kinetics in Iridium Complexes Catalyzing SABRE Nuclear Spin Hyperpolarization.

Large signal enhancements can be obtained for NMR analytes using the process of nuclear spin hyperpolarization. Organometallic complexes that bind parahydrogen can themselves become hyperpolarized. Moreover, if parahydrogen and a to-be-hyperpolarized analyte undergo chemical exchange with the organometallic complex it is possible to catalytically sensitize the detection of the analyte via hyperpolarization transfer through spin-spin coupling in this organometallic complex. This process is called Signal Amplification By Reversible Exchange (SABRE). Signal intensity gains of several orders of magnitude can thus be created for various compounds in seconds. The chemical exchange processes play a defining role in controlling the efficiency of SABRE because the lifetime of the complex must match the spin-spin couplings. Here, we show how analyte dissociation rates in the key model substrates pyridine (the simplest six-membered heterocycle), 4-aminopyridine (a drug), and nicotinamide (an essential vitamin biomolecule) can be examined. This is achieved for the most widely employed SABRE motif that is based on IrIMes-derived catalysts by 1H 1D and 2D exchange NMR spectroscopy techniques. Several kinetic models are evaluated for their accuracy and simplicity. By incorporating variable temperature analysis, the data yields key enthalpies and entropies of activation that are critical for understanding the underlying SABRE catalyst properties and subsequently optimizing behavior through rational chemical design. While several studies of chemical exchange in SABRE have been reported, this work also aims to establish a toolkit on how to quantify chemical exchange in SABRE and ensure that data can be compared reliably.

Energy transfer and conversion in the Allam cycle with a multi-stream heat exchanger

The Allam cycle is renowned for its high efficiency and low emissions in power generation, utilizing supercritical carbon dioxide as the working fluid. The regenerator, one of the key heat exchangers, plays a crucial role in the system. However, modeling the regenerator is challenging due to the presence of multiple pinch points. This study proposes a regenerator model that employs three multi-stream heat exchanger modules in Aspen Plus. A thermodynamic and economic analysis of the system was conducted and compared with a conventional system utilizing the two multi-stream heat exchanger modules. Simulation results show that the combustion chamber has the highest exergy loss in the system, accounting for 46.9 % of the total exergy loss. The turbine is identified as the most capital-intensive component, representing 44.9 % of the total equipment investment. Furthermore, a sensitivity analysis was conducted on key parameters. The results indicate that under certain operating conditions, the heat provided by the air separation unit is insufficient to reduce the temperature difference at the hot outlet of the regenerator. Compared to the conventional Allam cycle system using the 2R model, the 2R model predicts deviations of up to 28.9 %. This proposed model provides a new approach for the efficient allocation of energy utilization in the multi-stream heat exchange process within the Allam cycle system.

Prevention of morphological change for (Ba,Sr)(Co,Fe)O3 cathodes by incorporating (Ce,Gd)O2 for intermediate-temperature solid oxide fuel cells

Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) generally exhibits superior cathode activity compared to La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) for intermediate-temperature solid oxide fuel cells (IT-SOFCs). However, the chemical stability of BSCF is inferior to that of LSCF. When BSCF cathodes are sintered at a high temperature of 1050 °C, performance was compromised due to the formation of (Ba,Sr)ZrO3 between the scandia-stabilized zirconia (ScSZ) electrolyte and gadolinia-doped ceria (GDC) interlayer. The oxide ionic conductivity of (Ba,Sr)ZrO3 was low, decreasing the cathode performance. Furthermore, the BSCF grains enlarged, and cobalt oxide formed due to BSCF decomposition, decreasing the active specific surface area. However, by incorporating GDC into the BSCF cathode, the morphology remained unchanged and cobalt oxide formation was prevented, despite (Ba,Sr)ZrO3 still forming. The performance of the cell with the BSCF-GDC composite cathode surpassed that with the BSCF cathode due to decreased polarization resistance attributed to the oxygen surface exchange and diffusion processes in the cathode.

Hydrogen–Water Isotope Catalytic Exchange Process Analysis by Simulation

The hydrogen–water isotope catalytic exchange process has been widely applied in the tritium-containing water treatment process. It can be compared and analyzed conveniently with process simulation software. In this study, the catalytic exchange process was simulated by Aspen Plus software (V11). According to the simulation results, the main reaction process was that HDO in the liquid phase converts into HD in the gas phase, and the reaction mainly occurred at the bottom of the column, exhibiting a two-orders-of-magnitude-higher reaction amount compared to that observed in the top section. Different side reactions occur at distinct positions along the column, exhibiting a reaction amount that is lower by one to two orders of magnitude compared to the main reaction and aligning in the same direction as the main reaction. The optimum operating temperature is 60~80 °C, with the best performance observed at 70 °C, because of the large reaction equilibrium constant and the suitable ratio of vapor to hydrogen (1:4~1:1.5) in the gas phase. The influence of the residence time was investigated by introducing reaction kinetic equations. The residence time should be more than 1 s to ensure an adequate reaction. The influence of operating conditions on the hydrogen–water isotope catalytic exchange process can be deeply investigated by process simulation, and more mass transfer process quantities can be obtained. It plays a promoting role in guiding the process design and condition optimization.

Water-Soluble Lead Sulfide Nanoparticles: Direct Synthesis and Ligand Exchange Routes.

Colloidal semiconductor nanoparticles (NPs) represent an emergent state of matter with unique properties, bridging bulk materials and molecular structures. Their distinct physical attributes, such as bandgap and photoluminescence, are intricately tied to their size and morphology. Ligand passivation plays a crucial role in shaping NPs and determining their physical properties. Ligand exchange (LE) offers a versatile approach to tailoring NP properties, often guided by Pearson's Hard-Soft Acid-Base theory. Lead sulfide (PbS), a semiconductor of considerable interest, exhibits size-dependent tunable bandgaps from the infrared to the visible range. Here, we present two methods for synthesizing water-soluble, polyvinylpyrrolidone (PVP)-coated PbS NPs. The first involves direct synthesis in an aqueous solution while utilizing PVP as the surfactant for the formation of nano-cubes with a crystal coherence length of ~30 nm, while the second involves LE from octadecylamine-coated PbS truncated nano-cubes to PVP-coated PbS NPs with a crystal coherence length of ~15 nm. Multiple characterization techniques, including X-ray diffraction, transmission electron microscopy, Fourier-transform infrared spectroscopy, and thermal gravimetric analysis, confirmed the results of the synthesis and allowed us to monitor the ligand exchange process. Our findings demonstrate efficient and environmentally friendly approaches for synthesizing PVP-coated PbS NPs.

Extremely Active and Robust Ir-Mn Dual-Atom Electrocatalyst for Oxygen Evolution Reaction by Oxygen-Oxygen Radical Coupling Mechanism.

A novel Ir-Mn dual-atom electrocatalyst is synthesized by a facile ion-exchange method by incorporating Ir in SrMnO3, which yields an extremely high activity and stability for the oxygen evolution reaction (OER). The ion exchange process occurs in a self-limitation way, which favors the formation of Ir-Mn dual-atom in the IrMnO9 unit. The incorporation of Ir modulates the electronic structure of both Ir and Mn, thereby resulting in a shorter distance of the Ir-Mn dual-atom (2.41 Å) than the Mn-Mn dual-atom (2.49 Å). The modulated Ir-Mn dual-atom enables the same spin direction O (↑) of the adsorbed *O intermediates, thus facilitating the direct coupling of the two adsorbed *O intermediates to release O2 via the oxygen-oxygen radical coupling mechanism. Electrochemical tests reveal that the Ir-SrMnO3 exhibits a superior OER's activity with a low overpotential of 207 mV at 10 mA cm-2 and achieves a mass specific activity of 1100 A gIr -1 at 1.5 V. The proton-exchange-membrane water electrolyzer with the Ir-SrMnO3 catalyst exhibits a low electrolysis voltage of 1.63 V at 1.0 A cm-2 and a stable 2000-h operation with a decay of only 15 μV h-1 at 0.5 A cm-2.

Photoswitchable Imines Drive Dynamic Covalent Systems to Nonequilibrium Steady States.

Coupling a photochemical reaction to a thermal exchange process can drive the latter to a nonequilibrium steady state (NESS) under photoirradiation. Typically, systems use separate motifs for photoresponse and equilibrium-related processes. Here, we show that photoswitchable imines can fulfill both roles simultaneously, autonomously driving a dynamic covalent system into a NESS under continuous light irradiation. We demonstrate this using transimination reactions, where E-to-Z photoisomerism generates a more kinetically labile species. At the NESS, energy is stored both in the metastable Z-isomer of the imine and in the system's nonequilibrium constitution; when the light is switched off, this stored energy is released as the system reverts to its equilibrium state. The system operates autonomously under continuous light irradiation and exhibits characteristics of a light-driven information ratchet. This is enabled by the dual-role of the imine linkage as both the photochromic and dynamic covalent bond. This work highlights the ability and application of these imines to drive systems to NESSs, thus offering a novel approach in the field of systems chemistry.

Analysis of Water Exchange Processes between Groundwater and Surface Water in the Usangu Plains, Tanzania

Analysis of Water Exchange Processes between Groundwater and Surface Water in the Usangu Plains, Tanzania