Net Economic Revenue Research Articles

Nutrients and Contaminants in Soils of Current and Former Oil Palm Production Systems from Indonesia

Palm oil production in Southeast Asia often occurs on nutrient-poor, acidic soils converted from primary forest. Both the agricultural conversion and the production of oil palm are subsidised in Indonesia. As well as depleting soil organic C and plant nutrients, agricultural production on these soils can result in the accumulation of trace elements (TEs)—including micronutrients and non-essential trace elements—from the use of TE-containing agrichemicals including phosphate fertilisers and Cu fungicides. We tested the hypothesis that palm soils will have lower C concentrations than forest soils, as well as accumulation of TEs including Cu, Zn and Cd. Soil samples from active and abandoned oil palm plantations in Sumatra, Indonesia, were analysed for general soil properties as well as TE concentrations. Soils were acidic and low in key nutrients, with production likely to be limited by deficiencies of N, P, K, Mg and Mo, present at some sites in mean concentrations as low as 0.021%, 118 mg kg−1, 778 mg kg−1, 1023 mg kg−1 and 0.095 mg kg−1, respectively. Mean organic C was lower (2.0–3.3%) than reported values in nearby forest soils (7.7%). Soils under palm production contained elevated levels of Cu, Zn, As and Pb up to 38, 91, 9.0 and 28 mg kg−1, respectively, likely due to agrichemical use. The correction of nutrient deficiencies in palm production would require significant fertiliser inputs, which would exacerbate TE accumulation and reduce the net economic revenue from oil production. Our data have shown that in the plantations we have sampled, soils have become degraded. These tropical, weathered, and naturally nutrient-poor soils are ill suited to intensive production that requires high ongoing nutrient inputs. These findings have implications for the sustainability of a regionally significant production system across Southeast Asia.

Design and optimization of organic Rankine cycle using different working fluids for recovering waste heat in reaction-separation process of cumene synthesis

Reaction and distillation separation processes are two indispensable operating units in the chemical industry. However, a large amount of waste heat can be produced due to the presence of the reaction and distillation processes with high-temperature nature. Thus, it is of great significance to improve the economic performances of the reaction-separation processes via recovering waste heat. In the work, the recovery of waste heat from different heat sources in the reaction and distillation processes using the organic Rankine cycle (ORC) system with different working fluids is investigated taking the cumene synthesis process as an example. First, two streams with higher temperature and larger flowrates from the reaction section and distillation section are determined as the driving heat sources, while the conceptual design of the ORC system assisted reaction-separation process is completed. And then, the operation parameters of the ORC system with two heat sources and eight working fluids including R113, R123, R245ca, R245fa, R600, R600a, R601, and R601a selected by heuristic rules are optimized, aiming to maximize the annual net economic revenues (NER) using the genetic algorithm. Following, the corresponding exergy analysis of the ORC schemes driven by two heat sources with different working fluids is performed. The results illustrate that the heat of heat sources from both reaction section and separation section should be utilized since the ORC system with mentioned eight working fluids can produce positive NER, and the stream from the reaction section is more suitable as the driving heat source of the ORC system compared to that from the distillation section due to higher temperature, greater flowrates, and the coexistence of both latent heat and sensible heat. Overall, working fluids R113 and R123 are the worthiest of consideration among mentioned eight working fluids in terms of NER produced and the thermodynamic efficiency (η) of the corresponding ORC system. However, the environmental damage factors of the working fluids R113 and R123 are not preferred compared to other working fluids. Comprehensively considering economic, environmental, and thermodynamic performances, R601 are the preferred working fluid to perform the recovery of waste heat from the cumene synthesis process using the ORC system. The corresponding NER are 17.98 × 104$/a and 1.90 × 104$/a, which are 9.78% and 5.00% lower than that of the ORC system using the most economic working fluid R113, and at least 8.44% (R601a) and 2.70% (R123) higher than that of the ORC system using other working fluids for two heat sources, respectively. The η of the ORC system with R601 as working fluid can reach 17.73% and 11.15% for two heat sources, respectively, are slightly lower than that of the ORC system using R113 (19.41%) and R123 (11.49%) as working fluids.

Biological and economic efficacy of cowpea-radish association fertilized with organic manure in diverse planting arrangements

Green manuring and the spatial arrangement of planting intercropped crops are manageable factors to increase the bioeconomic effectiveness of intercropped systems. Therefore, the object of this study was to work out the bio-economic efficacy in cowpea-radish association under diverse Calotropis procera biomass amounts and planting arrangements in two cultivation seasons through biological and economic indices. The research was conducted in a design of randomized complete blocks with four repetitions. The treatments were made of combination of four C. procera biomass amounts placed into the soil (20, 35, 50 and 65 t ha-1) with three cowpea-radish planting arrangements (2:2, 3:3 and 4:4). The biological indices, land equivalent ratio (LER), area-time equivalency ratio (ATER), actual yield loss (AYL), and system productivity index (SPI) and the economic indicators gross revenue (GR), net revenue (NR), rate of return (RR) and profit margin (PM) were evaluated to express the bio-economic efficacy of the cowpea-radish association. The greatest biological efficiencies of the cowpea-radish association were attained with LER and ATER of 1.75 and 1.25; AYL and SPI of 1.48 and 13.15 t ha-1, respectively, in the amount of 62 t ha-1 of C. procera biomass in the planting arrangements 2: 2 and 3: 3. The largest net economic revenue (NR) of 16,382.85 R$ ha-1 was attained in the amount of 52 t ha-1 of C. procera in the planting arrangement 3: 3.

Optimal harvesting for a stochastic competition system with stage structure and distributed delay

A stochastic competition system with harvesting and distributed delay is investigated, which is described by stochastic differential equations with distributed delay. The existence and uniqueness of a global positive solution are proved via Lyapunov functions, and an ergodic method is used to obtain that the system is asymptotically stable in distribution. By using the comparison theorem of stochastic differential equations and limit superior theory, sufficient conditions for persistence in mean and extinction of the stochastic competition system are established. We thereby obtain the optimal harvest strategy and maximum net economic revenue by the optimal harvesting theory of differential equations.

Reaction-Separation Process Integration and Working Fluid Optimization for Organic Rankine Cycles Recovering Waste Heat in Cumene Synthesis

Reaction and distillation separation processes are two significantly energy-intensive unit operations in the chemical industry. Due to the high-temperature reaction and separation conditions, a large amount of waste heat with multiple grades is produced, which should be effectively utilized. In the article, the organic Rankine cycle (ORC) system is adopted to recover the waste heat in the reaction-separation process of cumene synthesis to generate electricity. The design parameters of the ORC system with eight working fluids including R113, R601, R123, R601a, R245ca, R245fa, R600 and R600a are optimized, aiming to maximize annual net economic revenues (NER) through the sequential quadratic programming (SQP). Simultaneously, the thermal efficiency (?ORC) of ORC system with optimal economic performance is calculated for eight working fluids. The results illustrate that R113 performs better than other working fluids in terms of NER and ?ORC. The corresponding annual net electricity generation (NEG), annual NER of ORC system (NERORC) and overall process (NERoverall) and ?ORC can reach 620.83 kW, 0.75 × 105 $/y, 2.11 × 105 $/y and 21.79 %.

Study of a Predator-Prey System with Monod-Haldane Functional Response and Harvesting

In the present work we study a predator-prey harvesting model with Monod-Haldane functional response. The mathematical features of the model have been analyzed in terms of stability, bifurcations and harvesting. Threshold values for some parameters indicating the feasibility and stability conditions of all equilibria are determined. The range of significant parameters under which the system admits different types of bifurcations are investigated. Optimal harvesting criteria and the net economic revenue are analyzed. Numerical illustrations are performed finally in order to confirm the analytical findings.

Bioeconomic model of zooplankton–phytoplankton in the central area of Morocco

Marine planktonic ecosystems are highly dynamic environments that are subject to a wide range of external forces. This paper presents the conditions for local and global stability of a bioeconomic problem concerning the harvesting of phytoplankton and zooplankton in Moroccan areas. The problem of determining the fishing effort that maximizes the net economic revenue of each fishing boat results in a generalized nash equilibrium problem. Growth of both organisms is governed by parameters as well as externally applied nutrients and the biomass of the other species available as supplemental nutrition. More precisely, we are interested in the equilibrium of the mathematical game given by the situation where all the fishing boats try to optimize their strategies according to the strategies of all the others. The importance of marine reserve is analyzed through the obtained results of the mathematical analysis of the proposed system.

Catchability coefficient influence on the fishermen's net economic revenues

The present paper describes a prey-predator type fishery model with two predators in competition. The aim of the paper is to maximize the net economic revenue earn from the fishery through implementing the sustainable properties of the fishery to keep the ecological balance. The existence of the steady states and the stability of the interior equilibrium point is studied using Routh Hurwitz criterion. The problem of determining the fishing effort that maximizes the net economic revenue of each fisherman results in a Generalized Nash Equilibrium Problem. More precisely, we are interested in equilibrium of mathematical game given by the situation where all fishermen try to optimize their strategies according to the strategies of all other fishermen. The importance of marine reserve is analyzed through the obtained results of the numerical simulations of proposed model system. The results depict that reserves will be most effective when the coefficient of catchability decreases.

Design and analysis of the novel concept of high temperature heat and power storage

A major portion of the electricity demand in Denmark is provided by wind farms. As wind power fluctuates sharply, there may be either surplus power or electricity deficit relative to the local demand. Thus, storing the surplus electricity and reclaiming it in demand times can increase the power plant incomes and reliability. On the other hand, as Denmark is one of the countries in which energy consumers are supplied by district heating, the demand for efficient and reliable heat production systems is also high. In this work, a novel and efficient energy storage system capable of providing both heat and electricity is designed and analyzed. This system is a smart combination of a thermal energy storage system and a gas turbine cycle without any combustion chamber. In order to have an optimal configuration, the system is designed based on thermodynamics criteria and net economic revenue. It is shown that the designed system may present an overall energy efficiency of about 90% and an electricity efficiency of approximately 35%. The economic assessment indicates that this innovative high temperature heat and power storage system, even taking into account conservative electricity and heat prices, is very profitable.

ECOLOGICAL SUSTAINABILITY OF AN OPTIMAL CONTROLLED SYSTEM INCORPORATING PARTIAL CLOSURE FOR THE POPULATIONS

This paper describes a prey–predator fishery model incorporating partial closure for the populations. It is assumed that the predator population partially dependent on a logistically growing resource with Beddington–De Angelis type functional response. The proposed system also reflects the dynamic interaction between the net economic revenue and the fishing effort used to harvest the populations. The steady states of the system are determined and the dynamic behavior of the system is discussed. The existence of Hopf bifurcation phenomenon is examined at the interior equilibrium point of the proposed system. We have adopted partial closure for the populations as a controlling instrument to regulate the harvesting of the populations. A dynamic framework towards the optimal utilization of the resource is developed using Pontryagin's maximum principle. The optimal system is numerically solved using an iterative method with Runge–Kutta fourth-order scheme. Simulation results show that the optimal control scheme can achieve a sustainable ecosystem. Results are analyzed with the help of graphical illustrations.

Reindeer management and winter pastures in the presence of supplementary feeding and government subsidies

We apply an age- and sex-structured reindeer-lichen model to examine the role of winter pastures, pasture rotation, and supplementary feeding on economically optimal reindeer management. The model includes 17 age classes of females, 13 classes of males and a detailed description of winter energy resource utilization by the reindeer population. Reproduction is specified by a modified harmonic mean mating system and the diet choice between different winter energy resources follows the principles of the optimal foraging theory. Wintertime energy intake defines an individual's weight decrease and its consequences on mortality and reproduction. Lichen growth depends on habitat type and lichen biomass. The decision variables are the animals chosen for slaughter from each age and sex class and the amount of supplementary food given. Results show that the availability of arboreal lichens, the growth rate of ground lichens, and pasture rotation all determine the optimal solutions. Reindeer management aiming to maximize long-term net economic revenues leads to very low lichen densities if intensive feeding becomes optimal in the long-term steady state. Government subsidies promote reindeer herders to base management on supplementary feeding leading to lower pasture conditions and to the depletion of lichens.

Ecological complexity and feedback control in a prey–predator system with Holling type III functional response

This article deals with a bioeconomic model of prey–predator system with Holling type III functional response. The dynamical behavior of the system is extensively discussed. Continuous type gestational delay of predators is incorporated in the system to study delay induced instability. It is observed that the system undergoes singularity induced bifurcation at interior equilibrium point when net economic revenue of the system increases through zero. State feedback controller is designed to stabilize the system at positive economic profit. Time delay is considered as a bifurcation parameter to prove the occurrence of Hopf bifurcation phenomenon in the neighborhood of the coexisting equilibrium point. Finally, some numerical simulations are carried out to verify the analytical results and the system is analyzed through graphical illustrations. © 2015 Wiley Periodicals, Inc. Complexity 21: 346–360, 2016

Stable coexistence mediated by specialist harvesting in a two zooplankton–phytoplankton system

This paper deals with a predator–prey model with specialist harvesting, representing a two predators (Zooplankton) and one resource (Phytoplankton) system. First, the existence and stability of equilibria is analyzed both from local and global point of view. Our results indicate that a specialist harvesting which is discriminate may mediate the coexistence of the two zooplankton species which competitively exclude each other in absence harvesting. Although in most cases increasing harvesting reduces the two zooplankton species numbers, when harvesting leads to coexistence, it may also lead to increase the two zooplankton species numbers. Furthermore, to protect fish population from over exploitation a control instrument tax is imposed. The problem of optimal taxation policy is then solved by using Pontryagin’s maximal principle. It is established that the zero discounting leads to the maximization of the net economic revenue to the society and an infinite discount rate leads to complete dissipation of the net economic revenue to the society. Finally, the impact of harvesting is mentioned along with numerical results to provide some support to the analytical findings.

Global Stability Analysis and Optimal Control of a Harvested Ecoepidemiological Prey Predator Model with Vaccination and Taxation

We propose an ecoepidemiological prey predator model, where selective harvest effort on predator population is considered. Vaccination and taxation are introduced as control instruments, which are utilized to control number of susceptible prey population and protect predator population from overexploitation, respectively. Conditions which influence nonnegativity and boundedness of solutions are studied. Global stability analysis around disease-free equilibrium is discussed based on robust Bendixson criterion, which is theoretically beneficial to studying coexistence and interaction mechanism of population within harvested ecoepidemiological system. By using Pontryagin’s maximum principle, an optimal control strategy is derived to maximize the total discounted net economic revenue to society as well as protect prey population from infectious disease. Numerical simulations are carried out to show the consistency with theoretical analysis.

Effort dynamics of a delay-induced prey–predator system with reserve

This paper describes a prey–predator fishery system with prey dispersal in a two-patch environment, one of which is a free fishing zone and the other a protected zone. The proposed system reflects the dynamic interaction between the net economic revenue and the fishing effort used to harvest the population in presence of a suitable tax. Local as well as global stability of the system is analyzed. The optimal taxation policy is formulated and solved with the help of Pontryagin’s maximal principle. The objective of the paper is to achieve the sustainability of the fishery, keeping the ecological balance, and maximize the monetary social benefit. The dynamical behavior of the delay system is further analyzed through incorporating discrete type gestational delay of predators, and the existence of Hopf bifurcation phenomenon is checked at the interior equilibrium point. Moreover, we use normal form method and center manifold theorem to examine the nature of the Hopf bifurcation. Theoretical results are verified with the help of numerical examples and graphical illustrations.

Economic perspective of marine reserves in fisheries: A bioeconomic model

The present paper describes a prey–predator type fishery model with prey dispersal in a two-patch environment, one of which is a free fishing zone and other is protected zone. The objective of the paper is to maximize the net economic revenue earn from the fishery through implementing the sustainable properties of the fishery to keep the ecological balance. Biological measures are introduced to increase the understanding of the mechanisms in the bioeconomic system. The importance of marine reserve is analyzed through the obtained results of the numerical simulations of proposed model system. The results depict that reserves will be most effective when coupled with harvesting controls in adjacent fisheries. The paper also incorporates the induced cost and premium from establishing a marine protected area in a fishery. It is found that premium of marine protected area (MPA) increases with the increasing size of the reserve. Results are analyzed with the help of graphical illustrations.

REGULATION OF A PREY–PREDATOR FISHERY INCORPORATING PREY REFUGE BY TAXATION: A DYNAMIC REACTION MODEL

This paper, describes a prey–predator fishery model incorporating prey refuge. The proposed model reflecting the dynamic interaction between the net economic revenue and the fishing effort used to harvest the prey species in the presence of predation and a suitable tax. The steady states of the system are determined and the dynamic behavior of the model system is discussed. The occurrence of Hopf bifurcation of the proposed model system is examined through considering density-dependent mortality for the predator as bifurcation parameter. The optimal taxation policy is formulated and solved with the help of Pontryagin's maximal principle. The objective of the paper is to maximize the monetary social benefit as well as prevent the predator species from extinction, keeping the ecological balance. Results are illustrated with the help of numerical examples.

A two-patch model for the optimal management of a fishing resource considering a marine protected area

In this work, we propose and analyze a model related with the management optimization of a renewable resource in aquatic environment composed of two different patches. Spatial distribution of each subpopulation is assumed: one is developed in a marine protected area (MPA) or a marine reserve and the other is located in a zone where fishing with open access may be effected. It is generally assumed that there may be migration between both areas, but in this work we will consider that the flux goes. When a fishing ban in the protected area is established it becomes a marine reserve, which can also be assumed as a refuge for the captured species. In this case, the marine reserve is the source and the exploitation area is a sink. The behavior of the renewable resource is modeled by a deterministic continuous time system. To establish the optimal harvesting policy, we will maximize the present value J of a continuous time stream of revenues, given by a cost functional indicating the net economic revenue to the fishermen, the perceived rent. Using Pontragyn’s Maximum Principle we will obtain the Hamiltonian function to determine the optimal policies.

CAPITAL THEORETIC ANALYSIS OF A HOLLING–TANNER-TYPE PREY–PREDATOR FISHERY WITH TAXATION AS A CONTROL INSTRUMENT

The level of fishing effort expands or contracts in a dynamic reaction model of a fishery accordingly as the net economic revenue (i.e. perceived rent) to the fishermen is positive or negative. A dynamic reaction model reflects this dynamic interaction between the perceived rent and the effort in a fishery. The combined harvesting of a prey–predator fishery is assumed to be regulated by an external authority by imposing a tax per unit biomass of both the species. The fishing effort is taken to be a dynamic variable of time, which is proportional to the instantaneous capital invested in the fishery. The steady states of the system along with their local as well as global stability are considered. The optimal harvesting policy with the tax as a control instrument is discussed. The results are numerically discussed and graphically illustrated. Sensitivity analysis of the parameters is carried out. The paper ends with concluding remarks.

Network impacts of distance-based road user charging

Distance-based road user charging is being seen as one potential mechanism to implement national road charging schemes. This paper investigates the design aspects of universal distance-based charging schemes and incorporates procedures within a detailed network supply model to represent how a range of different permutations of distance-based charges across a given network (charging regimes) affect route-choice, travel characteristics and demand for road space. The results suggest that distance-based charging can reduce number and length of trips, congestion, accidents and pollution, and provide net economic benefits and revenues. However, these benefits are not found to be uniform throughout the network. Their magnitude largely depends on the charge level, the hierarchy of charges across the network, and the difference between the charge levels.