Equilibrium Type Model Research Articles

A Synthesis on Impact Assessment Models from the Perspective of Evolution of the EU Common Agricultural Policy

Purpose: This paper aims to provide a comprehensive analysis of the current quantitative impact assessment methodologies, examining their strengths and weaknesses in terms of data requirements, as well as their consideration of social, economic, and environmental factors. Furthermore, it aims to elucidate the necessity for new-generation agricultural impact assessment models to incorporate advancements in information technology, communication tools, and big data analytics. Design/Methodology/Approach: In this review, the term "agricultural modelling platforms" is used to denote different equilibrium models and these models are divided into two categories according on their methodological approaches. The first category adopts a "systems approach," which includes general and partial equilibrium type models, as well as sector models. The "agent-based approach" is used by the second category. This review, thus, is primarily concerned with contrasting farm-representative models with farm-based models. Findings: The study emphasizes the importance of methodology and criteria in modelling exercises, considering factors like analysis level, environmental impact, and relationship between agriculture and the environment. It suggests that selecting the right modelling scale and tool requires asking the right research questions in advance. Originality/Value: In this study, general and partial equilibrium models, which allow impact analysis of policies implemented in the agricultural sector, which is increasingly faced with ecological and social problems, and Agent Based Models (ABM), which allow the problems in question to be included in the models, are compared and provided guidance to policy makers. It is aimed to reveal their advantages/disadvantages against each other. The originality of this study is that this comparison is made by taking into account the evolution of the European Common Agricultural Policy (CAP) since its establishment.

A Synthesis on Agent-Based Impact Assessment Models from the Perspective of the EU Rural Development Policy Measures

The second pillar of the EU’s CAP aims to support rural areas by meeting economic, environmental, and social challenges. To deal with these challenges, countries are faced with the question of selecting the best tools among a large set of policy instruments. The problem of choosing the best policy instruments is aggravated by the very heterogeneous nature of the societal demands that differ among member countries with very different economic and institutional structures. So far, policy impact assessment regarding the agricultural sector and rural areas has been carried out by partial and general equilibrium type models, sector models, and econometric approaches. In comparison to the above-mentioned sector/region/country-based platforms, the use of agent-based approaches, which consider spatial, social, and economic heterogeneity and the risk behavior of farms, has increased recently. From the above perspective, this paper first reviews the EU’s evolution of rural development policies and then compares some agent-based platforms used for agricultural policy impact assessment. To conclude, although specific features of agent-based models may provide several advantages over other modeling approaches, they still embody various problems, especially in terms of database adjustments and parameterization and calibration of the model.

Effects of Light, N and Defoliation on Biomass Allocation in Poa annua.

Plants allocate biomass to above- and below-ground organs in response to environmental conditions. While the broad patterns are well-understood, the mechanisms by which plants allocate new growth remain unclear. Modeling approaches to biomass allocation broadly split into functional equilibrium type models and more mechanistically based transport resistance type models. We grew Poa annua plants in split root boxes under high and low light levels, high and low N supplies, with N supplied equally or unequally. Our data suggest that light level had the strongest effect on root mass, with N level being more important in controlling shoot mass. Allocation of growth within the root system was compatible with phloem partitioning models. The root mass fraction was affected by both light and N levels, although within light levels the changes were primarily due to changes in shoot growth, with root mass remaining relatively invariant. Under low light conditions, plants exhibited increased specific leaf area, presumably to compensate for low light levels. In a follow-up experiment, we showed that differential root growth could be suppressed by defoliation under low light conditions. Our data were more compatible with transport resistance type models.

Travelling wave solutions for the Richards equation incorporating non-equilibrium effects in the capillarity pressure

The Richards equation is a mathematical model for unsaturated flow through porous media. This paper considers an extension of the Richards equation, where non-equilibrium effects like hysteresis and dynamic capillarity are incorporated in the relationship that relates the water pressure and the saturation. The focus is on travelling wave solutions, for which the existence is investigated first for the model including hysteresis and subsequently for the model including dynamic capillarity effects. In particular, such solutions may have non monotonic profiles, which are ruled out when considering standard, equilibrium type models, but have been observed experimentally. The paper ends with numerical experiments confirming the theoretical results.

A new mixed‐mode model for interpreting and predicting protein elution during isoelectric chromatofocusing

Experimental data are combined with classic theories describing electrolytes in solution and at surfaces to define the primary mechanisms influencing protein retention and elution during isoelectric chromatofocusing (ICF) of proteins and protein mixtures. Those fundamental findings are used to derive a new model to understand and predict elution times of proteins during ICF. The model uses a modified form of the steric mass action (SMA) isotherm to account for both ion exchange and isoelectric focusing contributions to protein partitioning. The dependence of partitioning on pH is accounted for through the characteristic charge parameter m of the SMA isotherm and the application of Gouy-Chapman theory to define the dependence of the equilibrium binding constant Kbi on both m and ionic strength. Finally, the effects of changes in matrix surface pH on protein retention are quantified through a Donnan equilibrium type model. By accounting for isoelectric focusing, ion binding and exchange, and surface pH contributions to protein retention and elution, the model is shown to accurately capture the dependence of protein elution times on column operating conditions.

Transport of Atrazine in Residue-Amended Soils

In this study, our aim was to quantify the transport of atrazine in soil columns where sugarcane (Saccharum spp. hyb.) residue was incorporated. The residue is a result of sugarcane combine harvest technology where massive amount of residue is deposited on the soil surface after each harvest. Miscible displacement experiments were carried out to quantify the mobility of atrazine in soil columns where sugarcane residue was mixed a Commerce soil. The residue was either incorporated uniformly with the soil or applied as a thin mulch layer over surface soil. The incorporation of residue with the soil resulted in retarded atrazine mobility because of strong sorption and slow release of the breakthrough curves (BTCs) during leaching. Moreover, early arrival of atrazine in the column effluent was observed from BTC results where the residue was uniformly incorporated with the soil, which is possibly due to physical nonequilibrium conditions, that is, preferential flow or macropore flow. An equilibrium-type model was incapable of describing atrazine BTCs from all columns regardless of whether the residue was placed as a surface layer or incorporated in the soil. In contrast, good overall description of measured BTC results was realized when a fully kinetic model was used. Therefore, our hypothesis that kinetic rather than equilibrium-type reactions are the dominant mechanisms for the release of adsorbed atrazine from the residue is supported.

Lyotropic Ion Channel Current Model Compared with Ising Model

Trans-membrane currents in ligand-gated ion channels are calculated in a non-equilibrium, chemically open whole cell system. The model is lyotropic in the sense that dynamics and parameters such as ligand concentration for half-maximal response (scale of response), and threshold for firing in neurons, are nonlinear functions of the reactant concentrations. The derived total current fits recorded data significantly better than those derived from mass action, Ising, and other equilibrium type models, in which the derived response can be displaced from the assessed response by several orders in the ligand concentration. A comparison of the model obtained with an Ising-like model provides a methodology to obtain the non-equilibrium scaling dependence of Ising-like models on the reactant concentrations.

Alachlor Transport during Transient Water Flow in Unsaturated Soils

In most herbicide mobility investigations, laboratory experiments are often restricted to the traditional miscible displacement methods where water saturated conditions and constant flux are maintained. In this study, we examine the mobility of alachlor herbicide under soil‐water unsaturated and transient conditions. Gigger (a Typic Fragiudalf) surface soil samples were collected from long‐term soybean management system under no‐till with wheat (NTW, Triticum aestivum L.), conventional tillage with wheat (CTW), and conventional tillage with hairy vetch (CTV, Vicia villosa Roth). Air‐dried soil was packed in columns which were horizontally maintained. The inflow end was connected to a water supply which was maintained at zero head. The input pulse was made up of tritium and 14C‐alachlor solution. During horizontal infiltration, the advance of the wetting front and volume infiltrated into the soil was monitored over time. When the wetting front reached 25 cm, the column was dismantled and the soil moisture and alachlor concentrations in each 1‐cm section quantified. All alachlor distribution profiles appeared retarded and did not show sharp solute fronts. Rather the concentration distributions were of moderately shaped fronts reaching some 10 cm from the source and followed by a gradual decrease up to 20 cm. Alachlor movement was modeled based on transient flow in unsaturated soils. Such results were compared with equilibrium type models of the linear and nonlinear type under steady and transient flow conditions. Parameters needed were soil water‐diffusivity, solute‐dispersion coefficients and retention parameters for alachlor for individual soils. Independently derived parameters provided a good description of the BTC under unsaturated conditions.

Structuring Deposit Insurance for a United Europe

This paper analyses the difficulties associated with imposing a unified deposit insurance scheme in a unified Europe. Specifically, it investigates the determinants of optimal deposit insurance in light of the Commission's 1994 decision requiring mandatory minimum coverage and encouraging a single unified deposit insurance structure. Issues of deposit insurance premiums and tax burden are analysed in the context of a general equilibrium-type model. The results indicate that taxes, the optimal degree of deposit insurance, and societal risk aversion are all interrelated in such a structure. Therefore, a common insurance system may not be feasible nor appropriate for a first best solution; co-ordination and even unified taxation may be necessary. At the minimum, exceedingly close macroeconomic policy co-ordination will be necessary for the single market for financial services to come to fruition and achieve stability.

Rationing, Queues, and Black Markets

Several types of rationing and queue mechanisms are compared in a framework of general equilibrium type models under gross substitutability and normality assumptions about consumers' Walrasian demand. During transition from rationing and queues to a market system, a group of low income people loses. The transition involves larger losses for this group if black markets prevail under rationing or queues, while a group of high income consumers gains. Some other comparative statics results are developed for a queue model with black markets. Copyright 1993 by The Econometric Society.

An Evaluation of Alternative Spatial Models

struct having space as one component.' Evaluation will be limited to economic models involving one or more commodities (primary, intermediate and/or final goods) and depicting one or more of the following economic activities: the regional location and level of production -including primary (farm) and/or secondary (processing) stages; shipping patterns of primary, secondary, and/or final goods; the regional level of consumption of final goods; and the relative and/or absolute level of regional prices. This includes formulations commonly called analysis models, interregional competition models, models, spatial equilibrium models, and plant location models. Model Classification and Description As the number of alternative models prohibits individual evaluation (without being too discriminating, one can list well over 500 separate formulations), they must be grouped according to some common characteristics. Although several meaningful classifications could be used, the usual distinction and the one followed here is to group the models into: standard equilibrium formulations using demand and supply relations and activity analysis models involving physical production activities and demand relationships. The two groups are not mutually exclusive-both may portray partial or complete equilibrium, their representation of shipping and consumption activities are similar, and the simplest model of each is the standard transportation model with preassigned regional quantities produced and consumed. In the standard equilibrium type model,2 discrete regions are defined and all production and/or consumption in each region is assumed to take place at one point (implicitly assuming homogeneity throughout the entire region). Quantities supplied and demanded in each region may be preassigned or a function of local prices and relevant exogenous variables, and unit transfer costs are specified between each producing and con