Equilibrium Approach Research Articles

Can paying politicians well reduce corruption? The effects of wages and uncertainty on electoral competition

We investigate the effects of wages and uncertainty on political corruption as measured by rent-taking. First, our laboratory data show that contrary to standard theory, rent-taking is not independent of, but decreases with wages in the absence of popularity shocks. Second, the orthodox view that rent-taking is greater in the presence of popularity shocks, given wages, is not necessarily true. Third, we find that in the presence of popularity or ideological shocks rent-taking is increasing in the variance of the shock for given wages, and is decreasing in wages for a given variance of the shock. While our third finding is in line with the directional predictions of the Nash equilibria, the deviation from Nash is large when the variance of the popularity shock is high and wages are low. We show that the deviations can be explained using a Quantal Response Equilibrium approach and taking risk-attitudes into account.

Development and Comparison of Thermodynamic Equilibrium and Kinetic Approaches for Biomass Pyrolysis Modeling

Biomass pyrolysis is considered as a thermochemical conversion system that is performed under oxygen-depleted conditions. A large body of literature exists in which thermodynamic equilibrium (TE) and kinetic approaches have been applied to predict pyrolysis products. However, the reliability, accuracy and predictive power of both modeling approaches is an area of concern. To address these concerns, in this paper, two new simulation models based on the TE and kinetic approaches are developed using Aspen Plus, to analyze the performance of each approach. Subsequently, the results of two models are compared with modeling and experimental results available in the literature. The comparison shows that, on the one hand, the performance of the TE approach is not satisfactory and cannot be used as an effective way for pyrolysis modeling. On the other hand, the results generated by the new model based on the kinetic approach suggests that this approach is suitable for modeling biomass pyrolysis processes. Calculation of the root mean square error (RMS), to quantify the deviation of the model results from the experiment results, confirms that this kinetic model presents superior agreement with experimental data in comparison with other kinetic models in the literature. The acquired RMS for the developed kinetic method in this paper varies within the span of 1.2 to 3.2 depending on temperature (400–600 °C) and various feedstocks (pine spruce sawdust, bagasse, wood bark, beech wood and paddy straw).

Low salinity water flooding: Evaluating the effect of salinity on oil and water relative permeability curves using coupling of DLVO and geochemical reactions

Enhancing the oil recovery of carbonate reservoirs with acidic oil depends on injected brine composition and salinity throughout the low salinity water flooding. The typical description of this phenomenon on oil and water relative permeability curves is being put forward by the process-dependent interpolation function, which barely addresses the underlying fundamentals governing the direct impact of wettability alteration and geochemical reactions on flow saturation functions. The main objective of this work is to perform an integrated investigation of the effect of salinity on oil and water relative permeability curves by dynamic coupling of the Derjaguin, Landau, Verwey, and Overbeek (DVLO) theory and geochemical reactions. We studied both the single and two-phase systems using the basis of the geochemical reactions to track the variations of the wetting and non-wetting phase relative permeability curves. In the single-phase scenario, the results show the superiority of the reactive flow modeling technique with kinetic-controlled reactions, in the range between [2–4] of the Damkohler number, to yield a better result for the experimental effluent ions' concentrations than the equilibrium approach. In addition, the single-phase results under dynamic conditions propose Civan correlation as the best predictor of residual resistance factor (RRF) by numerically adjusting the correlation of coefficients based on the physical variables - salinity, dimensionless consumed ion concentration, and Peclet number. Accordingly, the results indicate a novel linkage between the single-phase and two-phase results in the sense that RRF under single-phase mode can be used to estimate the change in the wetting phase relative permeability under the two-phase mode. The single-phase methodology provides the capability for an improvement – up to 15% - in the prediction of the pressure drop curve. For two-phase cases, our procedure involved coupling the characterized geochemical reactions and the DLVO theory to consider the effect of injected water composition on contact angle as the static two-phase parameter. The phase-field method is coupled with DLVO theory to calculate the relative permeability curves for the non-wetting phase, which corresponds to the contact angle at each simulation time step. The two-phase results indicate an improvement – up to 30% - in the prediction of the recovery factor curve, on a history-matching basis, using the DLVO theory with contact angle-dependent correlation of non-wetting phase relative permeability curve. The main novelties of this study are using the single-phase dynamic permeability impairment results in calculating the variation of the wetting-phase relative permeability curve. Moreover, dynamic coupling of DLVO and non-linear contact angle-dependent correlation is used to calculate the non-wetting phase relative permeability curve. According to these novelties, more accurate prediction of the laboratory production profiles can be obtained.

Cut slope stability assessment along forest roads using the limit equilibrium approaches and Slide software

Calculating the factor of safety (FS) as slope stability factor is necessary to prevent environmental damage. Therefore, this paper aims to (i) calculate FS using the limit equilibrium approaches and Slide software and (ii) investigate the stability of slopes according to calculated FS (Janbu and Bishop methods) and status of different sites in the study area (Hyrcanian forest of Iran). Six landslides were selected along the forest road by a field survey. Landslide dimensions including length, width, and height were measured using meters. Slope gradients were measured using the Suunto clinometer. The Slide software was used to evaluate the stability analysis of slopes. According to laboratory tests on soil samples the average of the liquid limit was recorded as 58%. The results of the direct shear test showed that the rate of soil cohesion (c) and coefficient of friction angle (φ) decreased with an increase in moisture content. According to the results, the factors of safety for landslide sites (Sites 1–6) were calculated to be 1.3, 0.65, 0.76, 0.55, 1.19 and 1.51, respectively. These calculated FS can accurately determine the slope status in terms of slope stability. According to the software classification, the status of Site 1 is “susceptible to landside”. Sites 2, 3 and 4 are “very high risk”. Also, the status of Sites 5 and 6 are “high risk” and “stable”, respectively. The instability of the slopes in studied sites is related to the drainage system (lack of culverts or ditches) as well as marlstone as bedrock. According to the calculated FS in different sites and comparison of the obtained results with the real conditions of sites, it can be concluded that the slope stability analysis in the Slide software is very accurate and it can be used to determine the factor of safety under different conditions in terms of morphology, hydrology and soil mechanics.

Microplane model of cylindrical geometry for transversely isotropic polymer composites

In this paper, a microplane model based on cylindrical geometry where the cylinder axis coincides with the longitudinal direction is developed for a general 3D inelastic fracturing analysis by finite element method of transversely isotropic fiber reinforced polymer composites. The model bridges the mesoscale material behavior to macroscale one using the stress equilibrium approach developed for cylindrical geometry. To this end, Microplane level stress–strain relations for tension, compression and shear for both longitudinal and transverse directions are formulated. An explicit algorithm is formulated and coded into a VUMAT user subroutine for use with ABAQUS. The model is suitable for the analysis and design of large structures made of fiber reinforced polymer composites unlike the competing mesoscale models because of its much lower computational cost. A detailed metodology for the calibration of the model is identified. The model is calibrated against the common test data available in the literature using this metodology and the predictive capacity of the model is demonstrated by comparing the model predictions with test data in longitudinal tension, lateral tension, longitudinal compression, lateral compression, longitudinal shear and rare size effect in bending tests including post-peak fracture available in the literature.

Seismic Stability and Liquefaction Analysis of Tailings Slope

The potential for liquefaction and slope stability of a thickened tailings slope, within a storage facility located on the shore of a natural glacial lake in Tehran, is evaluated based on field and laboratory testing. The tailings slope has the particularities of being located in a high seismicity area and founded on conventional slurry tailings from the previous operation of the facility. The in-situ state of the thickened tailings was investigated through field tests, including Standard Penetration Tests (SPT) and Cone Penetration Tests with pore pressure measurement (CPTu). Samples collected during the field investigation were used in an extensive geotechnical laboratory program to determine index properties and strength parameters for the thickened tailings. Testing included a series of isotropically consolidated undrained and drained (CIU and CID) triaxial tests, as well as a simulation of the consolidation process within the tailings through oedometer tests. The liquefaction potential was evaluated using the data from the CPTu testing, while slope stability was assessed using the limit equilibrium approach for an infinite slope, considering the variation of shear strength with the degree of consolidation (void ratio) of the tailings from a critical state approach. Based on the results of the liquefaction potential and the slope stability assessment, a design approach is suggested for facilities under similar conditions.

Modelling reservation-based shared autonomous vehicle services: A dynamic user equilibrium approach

Shared Autonomous Vehicles (SAVs) are expected to be used for regular and pre-planned trips. Such trips are suitable for reservation-based services, wherein the customer needs to book for a trip in advance. Systems enabling reservation of trips can allow for better planning of routes and schedules, and if optimally designed, enable higher efficiency. The primary objective of this research is to model the effects of such a system, by formulating and solving the combined Dynamic User Equilibrium and Shared autonomous vehicle Chain Formation (DUESCF) problem. The problem is formulated as a bilevel model based on game theory, involving road users and SAV service operator. Given a situation where conventional private and shared autonomous vehicles co-exist, road users select paths and departure times to maximize a perceived utility (commonly treated as minimizing a disutility) by forming a DUE (fixed point problem), and the SAV service operator tries to maximize the performance by forming appropriate SAV chains (combinatorial problem). The final objective of this bilevel model is a traffic assignment that includes SAV chain formation, such that both road users and SAV service operator obtain optimal solutions by reaching a Nash equilibrium, where no player is better off by unilaterally changing their decisions. A solution approach, based on Iterative Optimization and Assignment (IOA) method, is proposed with path flow and SAV performance changes as convergence criteria. Furthermore, the solution approach is tested for its robustness, and a scenario analysis is carried out to evaluate the impacts of reservation-based SAV services. The results show that a ridesharing SAV system is better compared to a carsharing and a mixed system consisting of both, in terms of total system travel time, congestion levels, total vehicle kilometres travelled and vehicle requirements.

Equilibrium and non-equilibrium molecular dynamics approaches for the linear viscoelasticity of polymer melts

Viscoelastic properties of polymer melts are particularly challenging to compute due to the intrinsic stress fluctuations in molecular dynamics (MD). We compared equilibrium and non-equilibrium MD approaches for extracting the storage (G′) and loss moduli (G″) over a wide frequency range from a bead-spring chain model in both unentangled and entangled regimes. We found that, with properly chosen data processing and noise reduction procedures, different methods render quantitatively equivalent results. In equilibrium MD (EMD), applying the Green−Kubo relation with a multi-tau correlator method for noise filtering generates smooth stress relaxation modulus profiles from which accurate G′ and G″ can be obtained. For unentangled chains, combining the Rouse model with a short-time correction provides a convenient option that circumvents the stress fluctuation challenge altogether. For non-equilibrium MD (NEMD), we found that combining a stress pre-averaging treatment with discrete Fourier transform analysis reliably computes G′ and G″ with a much shorter simulation length than previously reported. Comparing the efficiency and statistical accuracy of these methods, we concluded that EMD is both reliable and efficient, and is suitable when the whole spectrum of linear viscoelastic properties is desired, whereas NEMD offers flexibility only when some frequency ranges are of interest.

Energy Recovery from Waste Paper and Deinking Sludge to Support the Demand of the Paper Industry: A Numerical Analysis

The recovery of fibres from waste paper (WP) and deinking sludge (DIS) reduces the stress on nature compared to the collection of virgin pulp for paper production. Moreover, if not recycled, WP and DIS are mainly landfilled and incinerated, being thus responsible for the release of greenhouse gases (GHGs) into the atmosphere. In this context, energy recovery from WP and DIS would contribute to increasing energy independence and improving waste management in the pulp industry. From a broader perspective, it would increase renewable energy generation, supporting the paper industry in reducing fossil fuel consumption and GHGs emissions, in line with the goals of the European Union (EU) Green Deal 2021. For these reasons, in the present study, the combined heat and power generation potentiality of WP–DIS blends through gasification in combination with an internal combustion engine is numerically assessed for the first time. The air gasification process is simulated by applying a restricted chemical equilibrium approach to identify the optimum operating temperature (850 °C) and equivalence ratio (0.2). Electrical and thermal energy generation potentiality, considering WP and DIS production in the EU in 2019, is estimated to be in the ranges of 32,950–35,700 GWh and 52,190–56,100 GWh, respectively. Thus, it can support between 25 and 28% of the electrical and 44–48% of the thermal energy demand of the paper manufacturing sector, reducing the CO2 emission in the range of 24.8–28.9 Gt.

Energy, exergy, and environmental analyses of a poly-generation system based on biomass gasification

In this research, an integrated renewable-based energy system consisting of a biomass gasifier is investigated to generate electricity, heating, hot water, and freshwater. The emission of the system is evaluated based on a thermodynamic equilibrium approach. The concentration of CO, CO2, and NOx in combustion products are evaluated to assessment of environmental impacts. The results show that the value of normalized CO2, CO, and NOx emission are 729.9 kg/MWh, 0.0053 kg/MWh and 6.354 kg/MWh, respectively. Analyses indicate that despite that the concentration of CO2 in the product has the highest value, the emission cost of NOx with 170.6 $/h is higher than other species due to the harmful effects of this kind of emission. Results indicate that the higher value of design parameters i.e., gas turbine inlet temperature (GTIT), biomass moisture content (BMC), gasification temperature, and combustion temperature result in a decrease in the sustainability index.

Nonlinear Distributed Model Predictive Control for multi-zone building energy systems

This paper presents a distributed Model Predictive Control (MPC) approach for multi-zone building energy systems based on nonlinear Modelica controller models. The method considers both thermal and hydraulic coupling among different building zones. The iterative and parallel distributed optimization approach builds upon an uncooperative approach for thermal coupling using the Nash equilibrium approach and a cooperative approach for the hydraulic coupling using the Alternating Direction Method of Multipliers (ADMM). Apart from thermal coupling through walls, the modeling takes thermal coupling through doors into account using a data-driven approach, which calculates the inter-zone air exchanges based on temperature differences between door-coupled zones. The hydraulic coupling enables consideration of interactions between the zones introduced by a shared, central Heating, Ventilation and Air Conditioning (HVAC) system. The distributed MPC framework is structured in an easy-scalable, plug-and-play composition, where local systems are automatically assigned to the global coordination scheme. The distributed MPC method is applied to a simulative nonlinear case study, consisting of a six-room-building Modelica model considering both thermal and hydraulic interactions. The benefits of the proposed approach are demonstrated and compared against centralized and decentralized control concepts in terms of energy consumption, discomfort and computation time.

A Nash Equilibrium Approach to the Brazilian Seasonalization of Energy Certificates

This paper presents a Nash equilibrium approach to model a non-cooperative game that takes place among Brazilian hydro-generating companies in the annual process called “seasonalization”. We have “remade” the seasonalizations that occurred in the period of 2013–2020 by using our model and comparing the financial outcomes with the current ones that resulted from the seasonalizations the generators made each year, with financial improvements in almost every year. By using the Nash equilibrium approach, it is possible to achieve optimal decisions concerning the seasonalization process that were not evident by using traditional methods. This approach is useful for companies willing to enhance their income and to improve their risk management by making better choices in seasonalization.

Study of Energy Valorization of Disposable Masks via Thermochemical Processes: Devolatilization Tests and Simulation Approach

The COVID-19 pandemic exacerbated the use of medical protective equipment, including face masks, to protect the individual from the virus. This work studies the feasibility of using these materials as fuel for thermochemical processes for the production of syngas. A preliminary physic-chemical characterization was made by means of moisture and ash determination, thermogravimetric analysis, X-ray fluorescence. Afterward, pyrolysis and gasification tests were executed in a laboratory-scale fluidized bed reactor with chirurgical and FFP2 masks investigating four temperature levels and three different operating conditions (fluidizing agents and dry/wet sample). A qualitative and quantitative analysis of condensable aromatic hydrocarbons in the produced gas, collected during the test campaign, was performed employing a gas chromatograph-mass spectrometer. The experimental data from the tests were used to propose a hybrid approach to simulate the gasification process, based on experimental laws for the devolatilization step and a thermodynamic equilibrium approach for char gasification. The resulting data were compared with a thermodynamic equilibrium model, showing that the new approach captures non-equilibrium effects always present in real gasifiers operation.

M(t)/M(t)/m(t)/C(t) and non-stationary hypercube models

Purpose – Verify the effect of the variation of the arrival and service rate during the day in detriment of the equilibrium analysis of the system.Design/methodology/approach – The models M(t)/M(t)/m(t)/C(t) and the non-stationary hypercube were approached considering the change in the number of servers over time.Findings – The study showed how the dynamic approach is more realistic than the equilibrium approach in systems where the variation of parameters is an important factor to be considered.Originality/value – Most studies involving queue systems are based on steady-state analysis of the operation of these systems. However, for certain queuing systems, variations in customer arrival rates, service times and other operating conditions occur within very short time intervals, which makes it difficult to effectively analyze the performance of these systems.Keywords - Queuing theory, M(t)/M(t)/m(t)/C(t) Model, Non-stationary models.M(t)/M(t)/m(t)/C(t) and non-stationary hypercube models.

Controlling the Shrinkage of 3D Hot Spot Droplets as a Microreactor for Quantitative SERS Detection of Anticancer Drugs in Serum Using a Handheld Raman Spectrometer.

Quantitative measurement is one of the ultimate targets for surface-enhanced Raman spectroscopy (SERS), but it suffers from difficulties in controlling the uniformity of hot spots and placing the target molecules in the hot spot space. Here, a convenient approach of three-phase equilibrium controlling the shrinkage of three-dimensional (3D) hot spot droplets has been demonstrated for the quantitative detection of the anticancer drug 5-fluorouracil (5-FU) in serum using a handheld Raman spectrometer. Droplet shrinkage, triggered by the shaking of aqueous nanoparticle (NP) colloids with immiscible oil chloroform (CHCl3) after the addition of negative ions and acetone, not only brings the nanoparticles in close proximity but can also act as a microreactor to enhance the spatial enrichment capability of the analyte in plasmonic sites and thereby realize simultaneously controlling 3D hot spots and placing target molecules in hot spots. Moreover, the shrinking process of Ag colloid droplets has been investigated using a high-speed camera, an in situ transmission electron microscope (in situ TEM), and a dark-field microscope (DFM), demonstrating the high stability and uniformity of nanoparticles in droplets. The shrunk Ag NP droplets exhibit excellent SERS sensitivity and reproducibility for the quantitative analysis of 5-FU over a large range of 50-1000 ppb. Hence, it is promising for quantitative analysis of complex systems and long-term monitoring of bioreactions.

Modeling energy depletion in rat livers using Nash equilibrium metabolic pathway analysis

The current gold standard of Static Cold Storage (SCS), which is static cold storage on ice (about + 4 °C) in a specialized media such as the University of Wisconsin solution (UW), limits storage to few hours for vascular and metabolically active tissues such as the liver and the heart. The liver is arguably the pinnacle of metabolism in human body and therefore metabolic pathway analysis immediately becomes very relevant. In this article, a Nash Equilibrium (NE) approach, which is a first principles approach, is used to model and simulate the static cold storage and warm ischemia of a proposed model of liver cells. Simulations of energy depletion in the liver in static cold storage measured by ATP content and energy charge are presented along with comparisons to experimental data. In addition, conversion of Nash Equilibrium iterations to time are described along with an uncertainty analysis for the parameters in the model. Results in this work show that the Nash Equilibrium approach provides a good match to experimental data for energy depletion and that the uncertainty in model parameters is very small with percent variances less than 0.1%.

Exact and approximate mean first passage times on trees and other necklace structures: a local equilibrium approach

In this work we propose a novel method to calculate mean first-passage times (MFPTs) for random walks on graphs, based on a dimensionality reduction technique for Markov state models, known as local-equilibrium (LE). We show that for a broad class of graphs, which includes trees, LE coarse-graining preserves the MFPTs between certain nodes, upon making a suitable choice of the coarse-grained states (or clusters). We prove that this relation is exact for graphs that can be coarse-grained into a one-dimensional lattice where each cluster connects to the lattice only through a single node of the original graph. A side result of the proof generalises the well-known essential edge lemma (EEL), which is valid for reversible random walks, to irreversible walkers. Such a generalised EEL leads to explicit formulae for the MFPTs between certain nodes in this class of graphs. For graphs that do not fall in this class, the generalised EEL provides useful approximations if the graph allows a one-dimensional coarse-grained representation and the clusters are sparsely interconnected. We first demonstrate our method for the simple random walk on the c-ary tree, then we consider other graph structures and more general random walks, including irreversible random walks.

Prediction of phase equilibrium between soybean biodiesel, alcohols and supercritical CO2 using artificial neural networks

In this paper, a non-conventional approach of modeling phase equilibrium was applied. An alternative tool, the artificial neural network (ANN) technique has been used for estimating transition pressures for two ternary systems at high pressures (CO2 + Biodiesel + Methanol) and (CO2 + Biodiesel + Ethanol). Temperatures, molar ratios, and compositions were utilized as input variables at ranges of 303.15 to 343.15 K, 4.30 to 15.62 MPa and 0.4 to 0.99, respectively. The databases taken from the literature were split into training, validating, and testing data. Multiple ANN structures were applied and the model with the lowest mean square error (MSE) was selected. The selected ANN model for the methanol system was a two-layered Feed-Forward Network and achieved a determination coefficient (R2) of 0.99878 and MSE of 0.01612. While the ethanol system was best described by an Elman Network presenting an R2 and MSE of 0.99359 and 0.06078, respectively. Results were then compared with Peng-Robinson models using van der Waals quadratic and Wong-Sandler mixing rules. The results showed a better agreement with experimental data than the thermodynamic models.

Critical review on local thermal equilibrium and local thermal non-equilibrium approaches for the analysis of forced convective flow through porous media

Scientific community from the field of thermo-fluidics have focused extensive attention towards investigating techniques of enhancing the heat transfer in varied thermal systems. One of the most suitable techniques for augmenting the heat transfer is incorporating porous medium into thermal systems. The transport processes through porous media, which consists of a fluid phase and a solid matrix, can be modelled by either considering both to be in thermal equilibrium or in thermal non-equilibrium. Hence, two different modelling strategies viz. local thermal equilibrium (LTE) model and local thermal non-equilibrium (LTNE) model have been employed by different researchers. In this work, a comprehensive review of the published literatures in respect of the modelling approaches used for determining the implications of embedding porous media in different thermal systems from the perspective of heat transfer and entropy generation has been presented. The effects of various key determinants on the fluid flow, heat transfer characteristics and entropy generation in thermal systems are discussed. This discussion is then followed by a critical assessment of the applicability of LTE and LTNE approaches. At the end, conclusions and recommendations about the less explored systems and the areas that needs further investigations are summarized.

Political shocks in foreign policy and international politics: an alternative approach

ABSTRACT Political shocks are used extensively in research on foreign policy and international politics yet the analysis of political shocks, as its own topic of study, remains underdeveloped, and especially so when compared to analyses of other key concepts in the field. What we do know about shocks primarily comes from work where the focus is typically on other phenomena driving the inquiry. In this effort we reconceptualize what is meant by political shocks, focusing on actual versus potential shocks, create a methodology for identifying actual political shocks, based on a punctuated equilibrium approach to foreign policy change, illustrate its utility with application to human rights violations by countries, and suggest at the conclusion a theoretical framework that may help to spur a more comprehensive approach to explaining political shocks effects for both interstate and intrastate politics.