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This paper proposes a novel piezoelectric energy harvester attached with a trailing-edge flap under various installation angles, for enhancing the aeroelastic vibration and improving the harvesting performance. The mathematical models of the fluid-structure-electric coupled fields are derived, the simulation models of the multi-physical coupled fields of the harvester system with various installation angle flaps are established, and the experimental prototypes of the harvester are fabricated. The influences of the flap installation angles on the flow field and output characteristics are investigated theoretically, numerically, and experimentally. The results demonstrate that the flap stiffness and damping coefficients exert less influence on vibration characteristics and harvesting performance. The flap at a certain installation angle alters the flow field, affects the flow pattern, restricts the vortex shedding, and offsets the aerodynamic force and moment. A decrease in the flap installation angles results in increasing the vibration response and output performance. The obtained numerical results are in good agreement with the experimental and theoretical values, which verifies the effectiveness of the simulation model. The maximum plunge amplitude is 0.029 m and the output voltage is 15.51 V at 17.74 m/s and an installation angle of 0o. The enhancement ratio of the output voltage at 0o is up to 148.6% over 45o, which achieves better harvesting performance. The designed harvester system powers indirectly the pedometer for 104 s at 13.58 m/s. This research offers an essential foundation for achieving better tradeoffs in energy harvesting and vibration suppressing by appropriately selecting the flap installation angle. [Display omitted] • This paper first proposes a novel energy harvester with various installation angle flaps. • Flap alters the flow field, restricts vortex shedding, and increases output characteristics. • The maximum harvested plunge amplitude is 0.029 m and the output voltage is 15.51 V. • The enhancement ratio of the output voltage at 0o is up to 148.6% over 45o. • The harvester drives indirectly the pedometer for 104 s at 13.58 m/s. [ABSTRACT FROM AUTHOR]

Sugarcane is one of the main commodities in the world economy. An important step in the sugarcane supply chain is the harvest stage, requiring the support of mathematical modeling and optimization tools. Integrating the process of choosing the areas for harvesting according to the sugarcane maturation with the formation of the harvesting fronts and associating them with machine relocation costs is challenging. This paper contributes with a novel integer mathematical model that considers these concerns using three conflicting objectives. The first is that the sugarcane should be harvested as close as possible to its maturity, considering the sugarcane should be harvested as close as possible to its maturity by considering a combined measure of temperature and time since planting. The second aims to minimize the number of harvest fronts. The third objective is to minimize the costs involved with the relocation of the harvesters that cut the cane. Different strategies for obtaining Pareto-optimal solutions were proposed using exact methods, including MIP start and a decomposition technique. In the worst case, solutions with tolerable integrality gaps were obtained (inferior to 3%) in less than 1.5 h. Computational tests in real case studies were conducted in the sugarcane industry in two countries, indicating strong trade-offs in the determined solutions. In the Brazilian case, harvesting as close to maturation as possible, for example, causes an increase of 158% in the number of harvest fronts and 47% in the transportation costs, considering the minimum values for these objectives. Other trade-offs were seen and discussed when one of the other objectives was prioritized. These different compromise solutions help the decision-makers choose the most appropriate harvesting schedule according to their preferences. • We propose a new MIP optimization model to determine the harvesting of sugarcane. • The model aims to optimize three conflicting objectives. • A new method of computing cane maturation is used: the concept of degree-days. • A procedure for determining Pareto solutions by exact methods is proposed. [ABSTRACT FROM AUTHOR]

In this paper, a mathematical model consisting of a prey-predator system incorporating infectious disease in the prey has been proposed and analyzed. It is assumed that the predator preys upon the nonrefugees prey only according to the modified Holling type-II functional response. There is a harvesting process from the predator. The existence and uniqueness of the solution in addition to their bounded are discussed. The stability analysis of the model around all possible equilibrium points is investigated. The persistence conditions of the system are established. Local bifurcation analysis in view of the Sotomayor theorem is carried out. Numerical simulation has been applied to investigate the global dynamics and specify the effect of varying the parameters. It is observed that the system has a chaotic dynamics. [ABSTRACT FROM AUTHOR]

In this paper, a Holling-Tanner predator-prey model with ratio-dependent functional response and non-linear prey harvesting is analyzed. The mathematical analysis of the model includes existence, uniqueness and boundedness of positive solutions. It also includes the permanence, local stability and bifurcation analysis of the model. The ratio-dependent model always has complex dynamics in the vicinity of the origin; the dynamical behaviors of the system in the vicinity of the origin have been studied by means of blow up transformation. The parametric conditions under which bionomic equilibrium point exist have been derived. Further, an optimal harvesting policy has been discussed by using Pontryagin maximum principle. The numerical simulations have been presented in support of the analytical findings. [ABSTRACT FROM AUTHOR]

In this paper, a fractional-order predator–prey mathematical model has been developed considering Holling type II functional response. Here, we have investigated the interaction dynamics of prey, middle predator and top predator. We assume that the middle predator consumes only the prey, and the top predator consumes only the middle predator. Here, the logistic growth of prey has been considered. Then, different possible equilibrium points of our proposed system are determined. The stability of our proposed system is investigated around the equilibrium points. Then, some numerical simulations results are presented for better understanding the dynamics of our proposed model. It is found that the fractional-order derivative can improve the stability of our proposed system. [ABSTRACT FROM AUTHOR]

Extending the results of a previous paper on the relationship between fish consumption and coronary heart disease, an optimal control approach is proposed in the present paper. The Pontryagin's minimum principle is used to characterize the optimal control, to minimize the population of susceptible individuals and also to reduce the mortality rate of coronary heart disease. A numerical simulation is carried out to show the impact of the proposed optimal control. Indeed, the model shows that the prevalence and mortality of coronary heart disease can be significantly reduced in a period of 10 years. [ABSTRACT FROM AUTHOR]

In this paper, we consider a kind of delayed Schoener's competition model with harvesting terms and impulsive effects. By means of Mawhin's continuation theorem of coincidence degree theory, some sufficient conditions are obtained for the existence of at least four positive almost periodic solutions for the above model. Further, by using the comparison theorem and constructing a suitable Lyapunov functional, the global asymptotic stability of the model is also investigated. To the best of the author's knowledge, sofar, the results of this paper are completely new. An example and numerical simulations are employed to illustrate the main results in this paper. [ABSTRACT FROM AUTHOR]

Abstract: Time series of optical satellite images acquired at high spatial resolution is a potentially useful source of information for monitoring agricultural practices. However, the information extracted from this source is often hampered by missing acquisitions or uncertain radiometric values. This paper presents a novel approach that addresses this issue by combining time series of satellite images with information from crop growth modeling and expert knowledge. In a fuzzy framework, a decision support system that combines multi-source information was designed to automatically detect the sugarcane harvest at field scale. The formalism that we used deals with the imprecision of the data and the approximation of expert reasoning. System performances were analyzed using a time series of SPOT-5 images. Results obtained were in substantial agreement with ground truth data: overall accuracy reached 97.80% with stability values exceeding 89.21% for all decisions. The contribution of fuzzy sets to overall accuracy reached 15.08%. The approach outlined in this paper is very promising and could be very useful for other agricultural applications. [Copyright &y& Elsevier]

This paper presents three species harvesting model in which there is one predator species and two others are prey species. We derive boundedness and equilibrium point for this system. Also we derive the stability of this system analytically. We find bifurcation for this system. We have derived the binomic equilibrium point by using Pontryagin's maximum principle (PMP). Presented are various suitable analytical and numerical examples with Maple 18 programming. [ABSTRACT FROM AUTHOR]

In this paper a new revised multi-choice goal programming (RMCGP-LHS) model is proposed to deal with uncertainty in sugar cane harvest scheduling for sugar and ethanol milling companies. The RMCGP-LHS model uses a weekly decision-making horizon and takes into account the time and condition of land management, cane cutting decisions, and agricultural logistics. Its objective is to obtain information in order to harvest sugar cane plots in the period closest to the highest saccharose levels, while also minimizing agro-industrial costs. The RMCGP-LHS model was applied to a real case sugar and ethanol mill, and its optimization has provided harvesting policies that were validated by the company’s managers. Besides that the RMCGP-LHS model is a very practical tool for simulating in a fast way different scenarios involving uncertainties on model parameters and helping the managers in decision making process in real time. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a class of singular Leslie–Gower predator–prey bioeconomic models with environment fluctuations and time delays is investigated. Local stability analysis of the model reveals that there is a phenomenon of singularity induced bifurcation due to variation of economic interest of harvesting. By choosing the delay as a bifurcation parameter, it is shown that the Hopf bifurcations can occur as the delay crosses some critical values. Then, the effect of a fluctuating environment on the singular stochastic delayed predator–prey bioeconomic model is discussed. Finally numerical simulations demonstrate that the amplitude of oscillation for population is enhanced when compared with the oscillation observed in the deterministic environment. [Copyright &y& Elsevier]

Abstract: In this paper, we propose a tritrophic predator–prey model with harvesting where the top-predator population is partially supported with alternative food. We report the consequences of providing alternative food to the top-predator in a top-predator harvested model. The extinction criterion for top-predator population, local stability of equilibrium points and persistence conditions are discussed theoretically. Pontryagins maximum principle is used to characterize the optimal control of harvesting. We have derived the condition of Hopf bifurcation by varying harvesting effort. The bifurcation diagrams of the system with respect to harvesting effort in presence of alternative food are given. Our analysis show that alternative food can prevent top-predator extinction risk at higher harvesting effort and plays a vital role for biological conservation of species. [Copyright &y& Elsevier]

A nutrient-phytoplankton-zooplankton model is established, where harvest effort on phytoplankton population and seasonal intrinsic growth of nutrient biomass are considered. Positivity and boundedness of solutions of model system are studied. By analyzing the characteristic equation of linearized system corresponding to the proposed model system, local asymptotic stability around interior equilibrium is studied, which reveals that interior equilibrium loses its stability at some critical value of predation rate. By utilizing Poincaré surface of section and computation of Lyapunov exponents, numerical experiments are performed to discuss the complex dynamical behavior of model system. Model system shows rich dynamic behavior including limit cycle and chaotic attractor due to variation of predation rate and seasonal intrinsic growth rate. Further numerical experiments show that reasonable harvesting has stabilizing effect on population dynamics that prevents chaotic behavior. Numerical simulations are carried out to show consistency with theoretical analysis obtained in this paper. [ABSTRACT FROM AUTHOR]

A kind of delayed predator-prey system with harvesting is considered in this paper. The influence of harvesting and delay is investigated. Our results show that Hopf bifurcations occur as the delay τ passes through critical values. By using of normal form theory and center manifold theorem, the direction of Hopf bifurcation and the stability of the bifurcating periodic solutions are obtained. Finally, numerical simulations are given to support our theoretical predictions. [ABSTRACT FROM AUTHOR]

Cultivation of microalgae to utilize CO2 and nutrients in the wastewater to generate biofuel products is a promising research objective. However, the process faces tremendous technical difficulties, especially the harvest of microalgae cells, an economically challenging step. Several researchers recently reported co-culturing of filamentous fungi with microalgae so that microalgae cells can be co-pelletized in order to facilitate the cell harvest. This algae pelletization via the filamentous fungi represents an innovative approach to address both the cost and sustainability issues in algae biofuel production and also has potential with direct commercial applications. This paper reviews the current research status in this area and some possible drawbacks of this method in order to provide some possible directions for the future research. [ABSTRACT FROM AUTHOR]

Abstract: Power harvesting techniques that convert vibration energy into electrical energy through piezoelectric transducers show strong potential for powering smart wireless sensor devices in applications of structural health monitoring. This paper presents an analytical model of the dynamic behavior of an electromechanical piezoelectric bimorph cantilever harvester connected with an AC–DC circuit based on the Euler–Bernoulli beam theory and Hamiltonian theorem. A new cantilevered piezoelectric bimorph structure is proposed in which the plug-type connection between support layer and tip-mass ensures that the gravity center of the tip-mass is collinear with the gravity center of the beam so that the brittle fracture of piezoelectric layers can also be avoided while vibrating with large amplitude. The tip-mass is equated by the inertial force and inertial moment acting at the end of the piezoelectric bimorph beam based on D''Alembert''s principle. An AC–DC converting circuit soldered with the piezoelectric elements is also taken into account. A completely new analytic expression of the global behavior of the electromechanical piezoelectric bimorph harvesting system with AC–DC circuit under input base transverse excitation is derived. Moreover, an experimental energy harvester is fabricated and the theoretical analysis and experimental results of the piezoelectric harvester under the input base transverse displacement excitation are validated by using measurements of the absolute tip displacement, electric voltage response, electric current response and electric power harvesting. [Copyright &y& Elsevier]

Abstract: Animal forage plays an important role in agriculture. To maintain the silage quality during storage, preserving it from decomposition by wrapping the harvested crop with plastic stretch film is crucial. Any failure in the preserving process permits the infusion of oxygen, which allows the growth of undesirable aerobic microorganisms and silage decomposition. To study the state of the silage, temperature inside the stack could be used as indicator of decomposition. However, no previous study has developed a model that can detect decomposition based on abnormal temperature variations inside a silage stack. The first objective of this paper was to develop a structured nonlinear model to estimate the dynamics of temperature variations measured by a wireless sensor network-based monitoring system (nRF95E) inside a silage bale and stack prior to the decomposition process. The requirement of a robust nonlinear model is that sensor nonlinearities that are inherent in nature are considered. The results showed that a Hammerstein-Wiener (HW) model with sigmoid network performed the best in terms of percentage of fit (91.70%) between the measured and simulated output. The second objective was to estimate the length of time required to detect the decomposition process after the airtight seal was punctured using the model. The error between the predicted model output and the sensor readings exceeded a preset threshold interval 17 days after the cover film was punctured and 9 days after the decomposition process was detected due to the odour released. [Copyright &y& Elsevier]

Abstract: This paper describes a prey–predator model with stage structure for predator and selective harvesting effort on predator population. The Holling type II functional response function is taken into consideration. All the equilibria of the proposed system are determined and the behavior of the system is investigated near them. Local stability of the system is analyzed. Geometric approach is used to derive the sufficient conditions for global stability of the system. The occurrence of Hopf bifurcation of the model system in the neighborhood of the co-existing equilibrium point is shown through considering maximal relative increase of predation as bifurcation parameter. Fishing effort used to harvest predator population is considered as a control to develop a dynamic framework to investigate the optimal utilization of the resource, sustainability properties of the stock and the resource rent earned from the resource. Pontryagin’s maximum principle is used to characterize the optimal control. The optimal system is derived and then solved numerically using an iterative method with Runge–Kutta fourth-order scheme. Simulation results show that the optimal control scheme can achieve sustainable ecosystem. [Copyright &y& Elsevier]

Abstract: This paper describes a prey–predator fishery model with stage structure for prey. The adult prey and predator populations are harvested in the proposed system. The dynamic behavior of the model system is discussed. It is observed that singularity induced bifurcation phenomenon is appeared when variation of the economic interest of harvesting is taken into account. We have incorporated state feedback controller to stabilize the model system in the case of positive economic interest. Fishing effort used to harvest the adult prey and predator populations is used as a control to develop a dynamic framework to investigate the optimal utilization of the resource, sustainability properties of the stock and the resource rent earned from the resource. Pontryagin’s maximum principle is used to characterize the optimal control. The optimal system is derived and then solved numerically using an iterative method with Runge–Kutta fourth-order scheme. Simulation results show that the optimal control scheme can achieve sustainable ecosystem. [Copyright &y& Elsevier]

Abstract: This paper is concerned with a delay differential equation model for the interaction between two species, the adult members of which are in competition, with stage-structure and harvesting of the mature and immature members of each species. The maturation delay for each species is modelled as a distribution, to allow for the possibility that individuals may take a different amount of time to mature. General birth and death rate functions are used. We find that the dynamics of the model depends largely on the birth and death functions, which depend on the total number of adults. We study the dynamics of our model analytically and we present results on the positivity and boundedness of the solutions, and global stability results are established for each equilibrium. [Copyright &y& Elsevier]

Abstract: In this paper, we study an eco-epidemiological model where prey disease is modeled by a Susceptible-Infected (SI) scheme. Saturation incidence kinetics is used to model the contact process. The predator population adapt switching technique among susceptible and infected prey. The prey species is supposed to be commercially viable and undergo constant non-selective harvesting. We study the stability aspects of the basic and the switching models around the infection-free state and the infected steady state from a local as well as a global perspective. Our aim is to study the role of harvesting and switching on the dynamics of disease propagation and/or eradication. A comparison of the local and global dynamical behavior in terms of important system parameters is obtained. Numerical simulations are done to illustrate the analytical results. [ABSTRACT FROM AUTHOR]

Abstract: The paper is based on the research of forestry experts’ systems funded by “National Tenth-Five-Year 863 Plan”. In the context of the collective forest rights system reforms, in order to enhance the technological support to the farmers in the fast-growing and high-yield poplar cultivation, and to satisfy the actual needs of related enterprises, the study focuses on the fast-growing and high-yield poplar plantation harvest model and related decision-making criteria. Taking Populus tomentosa Carr as an example, by adopting the age–diameter at breast height growth model, diameter and tree height model, and the dual volume model based on Hebei Province’s data, the age–volume produce model is constructed; by adopting market price of the non-discount method which is relatively easy for farmers, PNW (Present Net Worth) and LEV (Land Expectation Value) calculation methods, the economic benefits evaluation model is established. By using the calculation results of these models as a decision-making benchmark, the growth model, evaluation model and a calculation example of Populus tomentosa Carr are obtained. Based on the above-mentioned studies, the components and functions, model base and model resolver algorithm of the system are designed, and the economic benefits forecast process is set. The result of the research is applied to the “National Eleventh-Five-Year Plan” funded program ”The research and application of key technologies in fast-growing and high-yield plantation production and management process informatization ”. And the application obtains a satisfied result. By using harvest evaluation system to conduct economic benefits analysis of poplar varieties, the farmers and the investors can predict future earnings and make decisions in reforestation. [Copyright &y& Elsevier]

Abstract: Maturity index (MI) is a key determinant of pea softness and ultimately retail value. Pea seed development goes through the optimal market stage for human consumption about a week before harvest. MI increases rapidly during the last 3–4 days prior to the optimal harvest which is when there is a need for better forecasting capability. Extensive field sampling is currently used to track MI in each of the individual paddocks, though it has limited ability to predict MI more than a day ahead. We developed an Artificial Neural Network (ANN) model that complements field sampling by forecasting the MI trend several days ahead. It was built using historical harvest information along with weather and climate forecasts. We implement and evaluate the ANN in a large pea growing region in Tasmania, Australia, and this paper highlights key results. The ANN produced an average error of 31.8MI units when forecasting MI at harvest with a 7-day lead time versus the current manual method which produced an average error of 36.6MI units for a lead time of 2 days. This means the model provides the ability to not only harvest peas closer to their ideal MI but also plan harvesting and transport logistics with a much greater lead time. [Copyright &y& Elsevier]

Abstract: In this paper, by employing the continuation theorem of coincidence degree theory, we establish an easily verifiable criteria for the existence of at least four positive periodic solutions for a discrete time delayed predator–prey system with nonmonotonic functional response and harvesting. [Copyright &y& Elsevier]

Recent studies involving selective coffee harvesting by shaking, indicates the necessity to apply to fruit -- stem system significantly high excitement frequencies in comparison with those that are habitually applied at the international practice. To reach the predicted frequency levels, in the order of 150-200 Hz, by mechanical, hydraulic or pneumatic means, is very difficult due to the presence of friction couples in these types of mechanisms that would suffer premature waste by the relative high speeds. It's for this reason that the development of electromagnetic vibrators in which the inertial mass, when moving inside a magnetic field, avoid the direct friction among kinematical couples, is a current task. In this paper, the mathematical modeling of a vibratory system of two degrees of freedom is made, using the method of the mechanical impedance, in order to obtain the frequency response of the system, and to determine the design parameters of a shaking device able to achieve certain levels of amplitude of the vibrations at the high required frequencies. From the study also emanates the conclusion that in such shaking device, the natural frequencies of the vibratory system should be contained in the range of the exciting force frequencies. [ABSTRACT FROM AUTHOR]

In this paper, we propose and analyse a mathematical model to study the dynamics of a fishery resource system in an aquatic environment that consists of two zones: a free fishing zone and a reserve zone where fishing is strictly prohibited. Biological and bionomic equilibria of the system are obtained, and criteria for local stability, instability and global stability of the system are derived. It is shown that even if fishery is exploited continuously in the unreserved zone, fish populations can be maintained at an appropriate equilibrium level in the habitat. An optimal harvesting policy is also discussed using the Pantryagin''s Maximum Principle. [Copyright &y& Elsevier]

Mathematical modeling and optimization was carried out in other to create and provide data for designing harvesting, processing, handling and storage machines or equipment using air for cleaning, sorting or separating pigeon pea seeds. Two varieties (Flavus and Bicolor) of pigeon peas seeds were conditioned from their initial moisture to 8, 10, 12, and 14% d.b, for the determination of terminal velocity and drag coefficient. Seeds samples of weight 50,100 and 150g were poured into a constructed air aerodynamic apparatus during the determination. A response surface method with an I-Optimal (IV) design was used to optimize and model both terminal and drag coefficient properties. The result obtained from the study for terminal velocity ranges from 5.2 to 11.98 m/s while that for drag coefficient ranges from 0.07 to 0.94. A reduced two factor interaction (R2FI) and reduce linear models was used for modeling data of terminal velocity and drag coefficient respectively. The two models was significant at p<0.01. The R2FI and Optimized values range for design consideration for harvesting machines were Moisture (13.52 - 14%), Weight (150g), Terminal velocity (11.67 - 11.98 m/s), Drag coefficient (0.18 - 0.21), Desirability (0.96 - 1.00). Those for processing and handling machines were Moisture (10 - 10.26 %), Weight (150g), Terminal velocity (7.65 0 8.2 m/s), Drag coefficient (0.42 - 0.44), Desirability (1.00). Finally those for storage structures and machines were Moisture (8%), Weight (150g), Terminal velocity (5.22 - 6.05 m/s), Drag coefficient (0.57), Desirability (1.00). [ABSTRACT FROM AUTHOR]