Equilibrium Model Research Articles

Adsorption of Cr(VI) and phosphate anions by amino-functionalized palm oil fibers.

This work developed a novel sustainable adsorbent (PF-Aq) prepared by the amino-functionalization of palm oil fibers (PF). XPS, SEM/EDS, TGA/DSC, and FT-IR techniques proved the successful functionalization of the PF with the amino group. The PF-Aq adsorbent presents a high adsorption capacity for phosphate and Cr(VI) ions. Adsorption kinetics of the ions onto the PF-Aq followed the general-order models, with 240- and 300-min equilibrium times for phosphate and Cr(VI), respectively. The Freundlich equilibrium model can explain the adsorption of phosphate and Cr(VI) on the PF-Aq. Besides, the maximum adsorption capacities were 151.07mgg-1 for phosphate and 206.08mgg-1 for Cr(VI). The best pH for the adsorption of both ions on PF-Aq was 4.0. Interestingly, adsorption was exothermic for phosphate and endothermic for Cr(VI). The adsorption capacities were reduced by 16% for phosphate and 10% for Cr(VI) after 5 adsorption-desorption cycles, demonstrating the good recyclability of the PF-Aq. It can be concluded that PF-Aq is a relevant adsorbent to uptake phosphate and Cr(VI) from water due to its high adsorption capacity, low cost, recyclability, availability, and fast kinetics. Finally, the excellent adsorption potential results from inserting amino groups in the PF, allowing electrostatic interactions between adsorbent and adsorbate.

Modelling stellar irradiances I: the transition regions of FGKM stars

ABSTRACT We employed advanced ionization equilibrium models that we developed in Dufresne et al. (2024), which include charge transfer and density effects, to model UV stellar irradiances for a sample of stars. Our sample includes $\epsilon$ Eridani (K2 V), $\alpha$ Centauri A (G2 V), Procyon (F5 V), and Proxima Centauri (M5.5 Ve). We measured line fluxes from STIS data sets and used O iv and O v as density diagnostics to find the formation pressure of ions in the transition region (TR) and adopted a simple differential emission measure (DEM) modelling. Our findings indicate significant improvements in modelling spectral lines from anomalous ions such as Si iv, C iv, and N v of the Li- and Na-like sequences, which produce the strongest lines in the UV. For example, the Si iv lines were under-predicted by a factor of 5 and now are within 40 per cent the observed fluxes. The improved models allow us to obtain for the first time reliable estimates of some stellar chemical abundances in the TR. We compared our results with available photospheric abundances in the literature and found no evidence for the first ionization potential (FIP) effect in the TR of our stellar sample. Finally, we compared our results with the solar TR that can also be described by photospheric abundances.

Governance and policy implications of the Inflation Reduction Act: A European perspective

AbstractThis paper examines the US 2022 Inflation Reduction Act (IRA) alongside the EU's Net‐Zero Industry Act (NZIA) and Critical Raw Materials Act (CRMA) of 2023. We analyze their differential approaches to accelerating investment in clean technology, enhancing energy security and fortifying supply chains. Both regions share the objective of diminishing reliance on Chinese dominance in clean industries. The US seeks to stimulate private investment primarily via uncapped tax credits from 2022 to 2031, some of them subject to stringent domestic content requirements. The EU has reacted to the potential violation of World Trade Organization's rules and a possible green investment shift to the US In doing so, the EU is relying heavily on a regulatory strategy, with emphasis on the simplification of procedures. However, the EU's public funding model is vague and leaves details to the discretion of member states, risking fragmentation within the single market. Through the application of a dynamic computable general equilibrium model, we show that a 50% increase in demand for the IRA's uncapped tax credits could nearly triple US GDP outcomes by 2027. We highlight the contrast between the IRA's immediate fiscal incentives and the NZIA's regulatory approach, emphasising that the former are more attractive for firms.

Water-Polymer Slide Electrification in Polyethylene Films Coated with Amphiphilic Compounds and Its Connection to Surface Properties Dependent on Water-Polymer Interactions.

Slide electrification experiments were performed on low-density polyethylene films (PE) and PE sprayed with five amphiphilic compounds, including antistatic and slip additives. Drops of aqueous solutions were delivered on the films and after sliding spontaneously acquired a net electrical charge (Qdrop), which is dependent on the pH and ionic strength. The slide electrification was detected in pristine PE films and those with five additives. An acid-base equilibrium model, based on the adsorption of hydroxides and protons on surface sites, accounted for the dependence of Qdrop on pH, allowing recovery of the acid-base equilibrium constants and the density of adsorption sites. The model was modified to account for ionic strength effects through activity factors. The surface conductivity, wettability, and friction coefficients were strongly modified by the additives. However, the observed trends are different from those observed in slide electrification, which better correlated with zeta potential determinations. This suggests that the interaction mechanisms among surface water, the considered additives, and the polymer, which are involved in slide electrification and the generation of zeta potential, are different from those associated with other surface processes involving surface water. Although additives are required for changing surface resistivity, friction coefficients, and wettability, the generation of sliding electrical charges in polyethylene is a spontaneous and highly effective process. For one specific additive, a simultaneous decrease in friction coefficients, zeta potential, and Qdrop was observed, assigned to the blockade of hydroxide adsorption sites and water repulsion by the compound.

Analysis of the exergy transfers in subcritical and transcritical CO[formula omitted] ejectors and their connection with the performance of the refrigeration cycle

Ejector refrigeration systems (ERSs) operating with carbon dioxide are notoriously challenging from both design and operation perspectives. In particular, the ejector itself gives rise to special attention since it directly affects the performance of the global system. In this study, the connections between local exergy transfers within the ejector and global cycle performance are investigated by using a novel multi-scale numerical approach. Computational Fluid Dynamics (CFD) is used to generate accurate predictions of the ejector operation with access to the local flow and heat transfer features. The exergy tube analysis is applied onto the simulation results, linking local transfers within the ejector to the results at the component- and cycle-scale. A state-of-the-art ejector thermodynamic model is then calibrated onto the CFD results, and employed to determine the physically possible operation of the ERS. In addition, the metastability impact on the exergy transfers and overall system performance is investigated by comparing the CFD results of the classical Homogeneous Equilibrium Model with those obtained with the Homogeneous Relaxation Model. Notably, it is found that at fixed ejector inlet conditions, there exits an outlet pressure that maximizes the exergy transfers from primary to secondary streams. Interestingly, this work shows for the first time that the maximum exergy gain of the secondary stream appears to correlate with the maximum coefficient of performance of the system, independently of the on- or off-design operation of the ejector. Moreover, metastability generally deteriorates the performance at both scales. The results of the present study serve to pave the way towards better ejector design objectives.

Estimating carbon leakage from aviation by combining sectoral and general equilibrium models

This article describes a procedure for estimating carbon leakage from policies targeting aviation based on alternative scenarios. The key innovation to ensure greater robustness is that all scenarios are simulated by two different types of models: a sectoral model for aviation and a computable general equilibrium model.•The implementation of scenario simulation in both models is explained•The calculation of carbon leakage is explained step by step

Possible development path for agricultural economic and trade cooperation in FTAAP: A numerical simulation

Exploring the path of developing agricultural economy and trade cooperation in the Free Trade Area of the Asia Pacific (FTAAP) is of great practical significance for deepening economic integration in the Asia Pacific region and strengthening regional agricultural development. This paper proposes three feasible paths based on RCEP, CPTPP, and the integration of RCEP and CPTPP to establish FTAAP. Moreover, a dynamic computable general equilibrium model of global trade is used to simulate the macroeconomic effects and the agricultural effects represented by China in forming FTAAP under these three paths. The research results show that six common policy nodes will promote macroeconomic growth in participating countries, and the effects of the in-depth implementation of RCEP and CPTPP will be greater than those of the initial implementation. Due to the broader base of participating economies and the higher level of openness, establishing FTAAP under Path 3 will yield greater macroeconomic effects and agricultural effects. Therefore, the path based on the integration of RCEP and CPTPP is an optimal selection for economic and trade cooperation of agriculture in FTAAP. All parties should actively overcome the obstacles to forming FTAAP and provide a stable internal and external industrial development environment for regional agricultural economic and trade cooperation.

Exploring the biosorption of nickel and lead by Fusarium sp. biomass: kinetic, isotherm, and thermodynamic assessment.

Fungal biomass is as a cost-effective and sustainable biosorbent utilized in both active and inactive forms. This study investigated the efficacy of inactivated and dried biomass of Fusarium sp. in adsorbing Ni2+ and Pb2+ from aqueous solutions. The strain underwent sequential cultivation and was recovered by filtration. Then, the biomass was dried in an oven at 80 ± 2°C and sieved using a 0.1-cm mesh. The biosorbent was thoroughly characterized, including BET surface area analysis, morphology examination (SEM), chemical composition (XRF and FT-IR), thermal behavior (TGA), and surface charge determination (pH-PZC and zeta potential). The biosorption mechanism was elucidated by fitting equilibrium models of kinetics, isotherm, and thermodynamic to the data. The biosorbent exhibited a neutral charge, a rough surface, a relatively modest surface area, appropriate functional groups for adsorption, and thermal stability above 200°C. Optimal biosorption was achieved at 25 ± 2°C, using 0.05g of adsorbent per 50mL of metallic ion solution at initial concentrations ranging from 0.5 to 2.0mg L-1 and at pH 4.5 for Pb2+ and Ni2+. Biosorption equilibrium was achieved after 240min for Ni2+ and 1440min for Pb2+. The process was spontaneous, mainly through chemisorption, in monolayer for Ni2+ and multilayer for Pb2+, with efficiencies of over 85% for both metallic ion removal. These findings underscore the potential of inactive and dry Fusarium sp. biomass (IDFB) as a promising material for the biosorption of Ni2+ and Pb2+.

Application of bursting pressure and conventional drained behavioural theory to the Brumadinho failure

The Brumadinho tailings dam failure in 2019 has had a profound impact on the way tailings engineers analyse and interpret stability, with the focus of assessments moving away from conventional drained behaviour to consideration of undrained and post-liquefaction resistance. One of the contributing reasons is that the Expert Panel investigation of the failure concluded that, despite the drained factor of safety being adequate, the failure took place in an undrained manner. This paper examines the Brumadinho failure from a conventional drained perspective using two-dimensional limit equilibrium and finite difference modelling. Collectively, these analyses show that the failure can also be explained by a drained triggering mechanism and therefore suggest that several additional lessons may be learnt from the failure.

Accurate Oil Temperature Prediction Model and Oil Refilling Parameters Optimization for Hydraulic Closed-Circuit System

Oil temperature plays a crucial role in hydraulic closed-circuit systems (HCS), and conventional thermal equilibrium models and coupled simulation models face challenges in terms of accuracy, efficiency, and cost when calculating oil temperature. This study introduces an innovative HCS oil temperature precise prediction model and oil refilling parameter optimization method. The initial sample space was determined through a Sobol sensitivity analysis and improved Latin hypercube sampling, leading to the development of a combinatorial agent model (CAM) suitable for oil temperature prediction with superior accuracy and stability compared to other methods. Based on CAM, the optimal oil refilling flow rates under various operational conditions are computed. To validate the efficacy of the theoretical analysis, an HCS experiment platform was established. The data indicates that the temperature prediction error range of the CAM model falls between 0.30 °C and 1.05 °C, and optimizing the oil refilling flow rate can effectively enhance system efficiency while ensuring that the oil temperature remains within permissible limits. The research methodology and findings are applicable in engineering practice and can be extended to optimize the design of other hydraulic systems.

Sojourning and Being Well Among Contemporary Chinese Gay Men in a Tourism Destination: An Extension of Dynamic Equilibrium Theory

This study proposes an extension of the dynamic equilibrium model to investigate the intrinsic mechanisms underlying the well-being experiences of Chinese gay tourists visiting Thailand. The enhanced model incorporates elements such as stock-challenge, flow-resource, and self-concept clarity, which illuminate the intrinsic dynamics of the inner well-being framework. Findings were derived from a video ethnography conducted collaboratively by researchers and participants. The results demonstrate that the impact of sojourning on well-being among gay Chinese travelers is influenced by their typical life and travel experiences, as well as the personalized meanings they associate with tourism and well-being. These responses are intricately shaped by their personal, social, and cultural contexts. This research provides rich insights into the holiday experiences and behaviors of contemporary Chinese gay adults, emphasizing the need for the development of tailored tourism policies and marketing strategies to cultivate gay-friendly destinations within the Asia region.

Subaerial Profiles at Two Beaches: Equilibrium and Machine Learning

AbstractShoreline position (e.g., beach width) is a critical component of flooding and overtopping forecasts but difficult to predict accurately. We model beach width changes with a supervised machine learning (ML) approach informed by equilibrium principles. The time history of wave energy anomalies that force equilibrium models is used as an ML input feature. The sweeping simplifying equilibrium model assumptions relating beach width change to anomalies are replaced with data‐based ML results. Supervised learning regression methods including linear, support vector, decision trees, and ensemble regressors are tested. Observations for model training and testing includes weekly to quarterly beach elevation surveys spanning approximately 500 m alongshore and 8 years at two beaches, each supplemented with several months of ∼100 sub‐weekly surveys. These beaches, with different sediment types (sand vs. sand‐cobble mix), both widen in summer in response to the seasonal wave climate, in agreement with a generic equilibrium model. Differences in backshore erodability contribute to differing beach responses in the stormiest (El Niño) year that are reproduced by a simple extra trees regression model but not by the equilibrium model. With sufficiently extensive training data, the ML model outperforms equilibrium by providing flexibility and complexity in the response to wave forcing. The present ML and equilibrium models both fail to simulate a uniquely stunted beach recovery unlike other recoveries in the training data.

Rigorous design and economic optimization of reactive distillation column considering real liquid hold-up and hydraulic conditions of industrial device

The liquid hold-up in a reactive distillation (RD) column not only has a significant impact on the extent of reactions, but also affects the pressure drop and hydraulic conditions in the column. Therefore, the liquid hold-up would be a critical design factor for RD columns. However, the existing design methods for RD columns typically neglect the influence of considerable amount of liquid hold-up in downcomers owing to the difficulties of solving a large-scale nonlinear model system by considering downcomer hydraulics, resulting in significant deviations from actual situation and even operation infeasibility of the designed column. In this paper, a pseudo-transient (PT) RD model based on equilibrium model considering tray hydraulics was established for rigorous simulation and optimization of RD plate columns considering the liquid hold-up both in downcomers and column trays, and a steady-state optimization algorithm assisted by the PT model was adopted to robustly solve the optimization problem. The optimization results of either ethylene glycol RD or methyl acetate RD demonstrated that assuming all the liquid hold-up of a stage belonged to the tray will cause significant deviations in the column diameter, weir height, and the number of stages, which leads to not meeting the separation requirements and even operation hydraulic infeasibility. The rigorous model proposed in this study which considers the liquid hold-up both on trays and in downcomers as well as hydraulic constraints can be applied to systematically design industrial RD plate columns to simultaneously obtain optimal operating variables and equipment structure variables.

An equilibrium model of reinsurance pricing

Reinsurance is the insurance of insurance companies. We develop a dynamic equilibrium model for reinsurance pricing based on the supply and demand of reinsurance. In the model, an insurance company and a reinsurance company make decisions on the optimal reinsurance policy as a demander and a supplier of reinsurance, respectively. The reinsurance price is determined when the demand matches the supply. We incorporate the proportional reinsurance policy as well as investment opportunities into the framework. The high flexibility of this equilibrium pricing model paves a new way for studies of optimal reinsurance and reinsurance pricing.

Adsorption and removal of herbicide paraquat from aqueous solutions via novel bimetal organic framework: Kinetics, equilibrium and statistical surface modeling

This study examines the adsorption and removal of the herbicide paraquat in relation to a bimetal organic framework known as the Terbium/Palladium Metal-Organic Framework (Tb/Pd-MOF). Analysis of N2 adsorption/desorption isotherms, which were used to assess the properties of the Tb/Pd-MOF, revealed that the absorption of paraquat on Tb/Pd-MOF resulted in a reduction in pore volume, pore size, and surface area. Specifically, the pore volume decreased from 8.25 to 5.68 cm3/g, the pore size decreased from 11.34 nm to 8.92 nm, and the surface area decreased from 1456.61 to 1262.82 m2/g. The pore radius also decreased from 0.96 nm to 0.58 nm. Tb/Pd-MOF’s functional groups were identified through FT-IR, and the structure of the compound was confirmed using XPS. Various adsorption parameters including temperature, adsorbent dosage, pH, paraquat concentration, and contact time were studied. Density functional theory (DFT) was used to understand the electrical properties, reactivity, and morphology of paraquat. Results from the DFT analysis revealed that the electrophilic and nucleophilic attack sites aligned with the molecular orbitals (HOMO and LUMO) and MEP outcomes. The study found that Tb/Pd-MOF demonstrated a significant absorption capacity for paraquat, with adsorption data consistent with the Langmuir isotherm and pseudo-second-order kinetic models. The paraquat adsorption capability of Tb/Pd-MOF was determined to be 574.8 mg/g. Furthermore, chemisorption was identified as the primary form of adsorption, as indicated by the adsorption energy of 26.98 kJ·mol−1. The optimal conditions for achieving a high adsorption capacity were identified as pH 8 and 0.02 g of Tb/Pd-MOF. The temperature-dependent changes in the thermodynamic parameters ΔG°, ΔH°, and ΔS° indicated that the paraquat absorption onto Tb/Pd-MOF occurred spontaneously, was endothermic, and involved random processes. To optimize the absorption process, Response Surface Methodology and Box-Behnken design (RSM, BBD) were employed. These techniques enabled effective removal of paraquat from the Tb/Pd-MOF material. During chemisorption, the adsorbate and adsorbent form chemical bonds, while aromatic rings are involved in π-π bonding. Additionally, pore-filling occurs when the adsorbate fills the pores of the adsorbent, and electrostatic interactions result from the attraction or repulsion of charges between the adsorbate and adsorbent. As a means of eliminating paraquat from wastewater, Tb/Pd-MOF demonstrates significant potential due to its diverse absorption processes and high capacity for adsorption.

Incorporating Model Uncertainty into Policy Analysis Frameworks: A Bayesian Averaging Approach Combining Computable General Equilibrium (CGE) Model with Metamodelling Techniques

Future sustainable economic development depends heavily on public policy at regional, national, and global levels. Therefore, it is essential to conduct a thorough policy analysis that ensures consistent and effective policy guidance. However, a major challenge in traditional policy analysis is the uncertainty inherent in the models used. Both policymakers and analysts face fundamental uncertainty regarding which model accurately represents the natural, economic, or social phenomena being analyzed. In this paper, we present a comprehensive framework that explicitly incorporates model uncertainty into the policy decision-making process. Addressing this uncertainty typically requires significant computational resources. We utilize metamodeling techniques to reduce computational demands. We illustrate the impact of various metamodel types by applying a simplified model to the CAADP policy in Nigeria. Our findings highlight that neglecting model uncertainty can lead to inefficient policy decisions and substantial waste of public funds.Copyright© 2024 The Author(s). This article is distributed under the terms of the license CC-BY 4.0., which permits any further distribution in any medium, provided the original work is properly cited.

The Imprint of Dark Matter on the Galactic Acceleration Field

Measurements of the accelerations of stars enabled by time-series extreme-precision spectroscopic observations, pulsar timing, and eclipsing binary stars in the solar neighborhood offer insights into the mass distribution of the Milky Way that do not rely on traditional equilibrium modeling. Given the measured accelerations, we can determine a total mass density and infer the amount of dark matter (DM) by accounting for the mass in stars, gas, and dust. Leveraging FIRE-2 simulations of Milky Way–mass galaxies we compare vertical acceleration profiles between cold DM (CDM) and self-interacting DM (SIDM) with a constant cross section of 1 cm2 g−1 across three halos with diverse assembly histories. Notably, significant asymmetries in vertical acceleration profiles near the midplane at fixed radii are observed in both CDM and SIDM, particularly in halos recently affected by mergers with satellites of Sagittarius/SMC-like masses or greater. These asymmetries offer a unique window into exploring the merger history of a galaxy. We show that SIDM halos manifest a more oblate shape and consistently exhibit higher local stellar and DM densities and steeper vertical acceleration gradients, up to 10%–30% steeper near the solar neighborhood. However, similar magnitude changes can arise from azimuthal variations in the baryonic components at a fixed radius and external influences like mergers, making it difficult to distinguish between CDM and SIDM using acceleration measurements in a single galaxy.

Feasibility study of underground CO2 storage through Water Alternative Gas (WAG) operation: A case study in Southwestern Ontario

Geological CO2 storage (GCS) offers a promising, low-risk, long-term solution for carbon sequestration. This study assesses the feasibility of GCS water-alternating-gas (WAG) operations in a brine formation targeted for the Western Ontario GCS plan. The Cambrian strata shows potential for CO2 storage but faces challenges like limited lateral extension and geopolitical issues from plume migration. To mitigate these risks, a deep evaluation of CO2 trapping mechanisms is crucial. CO2 dissolution into brine provides secure storage by reducing the free plume. The proposed WAG operation promotes dissolution, using a vertical equilibrium model coupled with a black oil model to estimate CO2 trapping proportions during and post-injection. The Taguchi design of experiments investigates various WAG scenarios with minimal simulations, reducing numerical costs. Sensitivity analysis/optimization of WAG parameters, including water extraction rate (WER), water injection rate (WIT), and CO2 injection time (CIT), ranked their effectiveness in CO2 dissolution. Optimal WAG operations can reduce the free plume by 49 % and increase the dissolution ratio from 0.26 to 0.52. CIT and WIT were found to be the most influential factors, contributing 42 % and 31 % to CO2 dissolution, and 43 % and 34 % to overall CO2 trapping, respectively, while WER exhibited a lower impact of 8–9%.

Employer-provided parking: Departure time choice, investment decision, and welfare effects

Employer-provided parking (EP) has become a prevalent way to reduce employees’ parking delays and late arrivals through offering them free or low-price parking spaces at the workplace. This paper explores the EP effects on employees’ trip scheduling, employer’s EP investment decision, and commercial parking operator’s pricing decision. An analytical trip scheduling equilibrium model is first presented to model the interaction between EP provision and employees’ departure time choices during morning commute. A profit maximization model incorporating the employee productivity is then developed to determine the employer’s optimal EP investment decision. A competitive game between employer’s investment decision and commercial parking operator’s parking pricing decision is analytically investigated, together with the effects of EP investment on social welfare. The results show that the EP investment can lead to a win-win situation with decreased employee commuting cost and increased firm production output; and the employer would like to provide only part of the employees with EP services. The competitive game solutions depend very much on the marginal costs of EP and commercial parking spaces. The EP investment with an excessively high commercial parking fee may hurt the society due to decreased social welfare.

Optimal Sin Taxation and Market Power

We study how market power impacts the efficiency and redistributive properties of sin taxation, with an empirical application to sugar-sweetened beverage taxation. We estimate an equilibrium model of the UK drinks market, which we embed in a tax design framework to solve for optimal sugar-sweetened beverage tax policy. Positive price-cost margins for drinks create inefficiencies that lower the optimal rate compared with a perfectly competitive setting. Since profits mainly accrue to the rich, this is partially mitigated under social preferences for equity. Overall, ignoring market power when setting tax policy leads to welfare gains 40 percent below those at the optimum. (JEL D62, H21, H23, H25, L13, L25, L66)