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Copyright of Journal of South China University of Technology (Natural Science Edition) is the property of South China University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Our study aimed to identify a design which would reduce cutting resistance during the harvesting of castor. This paper presents a theoretical study of the wave-type disc cutter, which plays an important role in castor harvesting. Based on the SPH–FEM coupling algorithm, a combined orthogonal rotation experiment was performed to study the effects of disc cutter thickness, edge angle, disc cutter rotation speed, and feeding speed on the maximum cutting force. The response surface method was used to achieve an optimal combination of all the test factors. Mathematical modeling of the maximum cutting force and influencing factors was utilized to obtain the optimal parameters for a cutting system consisting of wave-type disc cutters. The optimal results were obtained with a computer-simulated disc cutter rotation speed of 844.2–942.1 r/min, a feeding speed of 0.89–1.01 m/s, a disc cutter thickness of 2.71–3.15 mm, and an edge angle of 29.2–33.9°. Under these conditions, the maximum cutting force was less than 50 N. Finally, the experimental data and numerical computer simulation results were compared using cutting performance test verification. The analysis found that the test results and simulation results were largely consistent. Therefore, the simulation model was judged to be effective and reasonable. [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]

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]

This paper presents a prey-predator harvesting model with time delay for bifurcation analysis. We consider the parameters of the proposed model with imprecise data as form of interval in nature, due to the lack of precise numerical information of the biological parameters such as prey population growth rate and predator population decay rate. The interaction between prey and predator is assumed to be governed by a Holling type II functional response and discrete type gestation delay of the predator for consumption of the prey under impreciseness of the biological parameters. Parametric functional form of interval number with two parameters is introduced. This study reveals that not only delay and harvesting effort play a significant role on the stability on the system but also interval parameters play a crucial role on the stability of the system. Computer simulations of numerical examples are given to explain our proposed imprecise model. We also address critically the biological implications of our analytical findings with proper numerical example. [ABSTRACT FROM AUTHOR]

Copyright of Iraqi Journal of Science is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

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, 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]

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]

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]

Harvesting models are needed within simulation studies to assess ‘business as usual’ scenarios in future stand development. Such models require data from repeated observations addressing the removals as they are based on specific silvicultural management regimes. The purpose of this paper was to develop and apply a harvesting model for uneven-aged single-tree forest management based on data from the forest company ‘Forstbetrieb Ligist, Souveräner Malteser Ritterorden’ in Austria. This company has been known for its transition from even-aged to uneven-aged forest management since the 1930s. Our harvesting model comprises two logistic functions to simulate a single-tree selection process: (1) predicting the probability of harvesting and (2) removal. The set of equations are tested and implemented in the tree growth model MOSES (MOdelling Stand rESponse). MOSES is used as a diagnostic tool to assess different forest management regimes. In this study, we are specifically interested in (1) evaluating the model by comparing predicted and observed removals and (2) predicting future stand development considering the current management practices—the business as usual as it can be derived from the harvesting model. The results suggest that in combination with MOSES, our model correctly mimics the growth development over time since no systematic trends between predicted and observed diameter growth at breast height classes are apparent. Furthermore, it is evident that by applying the current plenter harvesting strategy, a constant stand basal area of ∼35 m2 ha–1 will be achieved. [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 study theoretically analyzed the cutting process of castor and determined the structural parameters of the key component of the castor disc-cutting device, aiming to obtain the optimal operation parameter combination and reduce the cutting resistance and power consumption during the harvesting process. The effects of the cutting-disc thickness, cutting-disc rotational speed, feeding speed, and edge angle on the cutting power consumption were studied using an orthogonal rotation combination experiment. The response surface method was used to optimize the parameters, and the mathematical relationship model between the cutting power consumption and each factor was established to determine the optimal parameter combination for disc cutting. The simulation results showed that the optimal combination of cutting parameters was cutting-disc thickness of 3 mm, cutting-disc rotational speed of 550 r/min, feeding speed of 0.6 m/s, and edge angle of 20°. Under these conditions, the cutting power consumption was 1.20375 J. The test results were basically consistent with the model prediction results. Therefore, this study provided a theoretical basis and reference for the design and improvement of castor harvesters. [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]

In this paper a new concept for modeling uneven-aged forests (UEAF) is presented. The term UEAF in this article encloses all forests that deviate from the even-aged structure. The matrix model is area-based, in that the forest under study is described by a distribution of areas over fixed state-spaces spanned by stem number and volume per hectare classes. Dynamics is introduced as transitions of areas inside the state-space during the simulation. Harvesting activities and the occurrence of calamities are explicitly handled. The model is designed to be suitable for large-scale analyses. The concept was tested in an application to Austrian National Forest Inventory (NFI) data. Results shown, including a comparison to older inventory data, indicate that it is worth further elaborating on the concept and the model. The work will be continued and in the next step the model concept will be applied in several other countries. [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 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]

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]

The main aim of this study was to optimize the design parameters of the fruit shakers for efficient harvesting of Shengy olive. A single-degree-of-freedom spring-mass model was established to determine the natural frequency and damping coefficient of the limb. A tractor-mounted shaker that transmits vibration to limbs and fruits via a reciprocating mechanism was fabricated for field evaluation of the forced vibration modes. A 3×4 factorial experiment with a completely randomized design was conducted to investigate the effects of shaking amplitudes and frequencies on fruit removal. The shaking mode with a frequency of 10 Hz and amplitude of 80 mm transmitted the average power of 92 W to remove 95% of fruits in the field trial. This oscillation characteristic should be used to redesign the fruit shakers to pass human safety standards and efficient harvesting. [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: There is a gap between single-species model predictions, and empirical studies, regarding the effect of habitat fragmentation per se, i.e., a process involving the breaking apart of habitat without loss of habitat. Empirical works indicate that fragmentation can have positive as well as negative effects, whereas, traditionally, single-species models predict a negative effect of fragmentation. Within the class of reaction-diffusion models, studies almost unanimously predict such a detrimental effect. In this paper, considering a single-species reaction-diffusion model with a removal – or similarly harvesting – term, in two dimensions, we find both positive and negative effects of fragmentation of the reserves, i.e., the protected regions where no removal occurs. Fragmented reserves lead to higher population sizes for time-constant removal terms. On the other hand, when the removal term is proportional to the population density, higher population sizes are obtained on aggregated reserves, but maximum yields are attained on fragmented configurations, and for intermediate harvesting intensities. [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]

The evolution of compliance with regulation and the evolution of a CPR stock are modeled jointly in a setup where replicator dynamics describing compliance with harvesting rules are combined with resource stock dynamics. This evolutionary approach suggests that in long-run equilibrium, coexistence of both cooperative and non-cooperative rules is possible under regulation. Stock effects on profits and a certain structure of auditing probabilities could imply the emergence of a limit cycle in areas of low stock levels, as an equilibrium outcome. It might be easier for the regulator to obtain full compliance under precommitment to fixed auditing probabilities. [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]

The purpose of this study is to explore an ecological Ammensal model with four species of Species- 1 i.e Ammensal Prey (PA), Species-2 i.e Ammensal Predator (QA), Species-3 i.e Ammensal Enemy (EA), and Species-4 i.e Enmity(N) with harvesting at variable rate(?). The System mainly consists of an Ammensal Prey (PA), a Ammensal Predator (QA) that survives on an Ammensal -prey(PA), Ammensal Enemy (EA) and Enmity(N) for which PA, QA are Ammensal, i.e., EA and N have an undesirable effect on PA and QA without being affected in any way. Furthermore, EA is enormous for N, and N is harmful to EA. First level Ammensalism is represented by the pair PA & EA, the pair of second level Ammensalism is QA & N and third level Ammensalism by the pair EA & N. The system's model equations form a set of four non-linear ordinary differential coupled equations of first order. There are sixteen equilibrium points found. The interactions between the four species are explored in light of different changes in various species' growth rate. [ABSTRACT FROM AUTHOR]

Provides information on a study concerning the development of a mathematical model for predation-prey metapopulation as a generalization of single-species metapopulation harvesting theory. Economic efficiency of predation and the protection of relative source prey; Observation concerning harvesting and seeding strategy.

We propose and study a nonautonomous harvesting Lotka-Volterra commensalism model incorporating partial closure for the populations. By using the differential inequality theory we obtain sufficient conditions that ensure the extinction, partial survival, and permanence of the system. By applying the fluctuation lemma we establish sufficient conditions that ensure the extinction of one of the components and the stability of the the other one. For the permanent case, by constructing a suitable Lyapunov function we obtain some sufficient conditions for the globally attractivity of the positive solution of the system. Examples, together with their numeric simulations, show the feasibility of the main results. To ensure the stable coexistence of the two species, the harvesting area should be carefully restricted. [ABSTRACT FROM AUTHOR]

Copyright of Lucrari Stiintifice, Universitatea de Stiinte Agricole Si Medicina Veterinara Ion Ionescu de la Brad Iasi, Seria Horticultura is the property of University of Agricultural Sciences and Veterinary Medicine (Editura Ion Ionescu de la Brad) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

First, a discrete stage-structured and harvested predator-prey model is established, which is based on a predator-prey model with Type III functional response. Then theoretical methods are used to investigate existence of equilibria and their local properties. Third, it is shown that the system undergoes flip bifurcation and Neimark-Sacker bifurcation in the interior of , by using the normal form of discrete systems, the center manifold theorem and the bifurcation theory, as varying the model parameters in some range. In particular, the direction and the stability of the flip bifurcation and the Neimark-Sacker bifurcation are showed. Finally, numerical simulations are presented not only to illustrate our results with the theoretical analysis, but also to exhibit the complex dynamical behaviors, such as cascades of period-doubling bifurcation and chaotic sets. These results reveal far richer dynamics of the discrete model compared with the continuous model. The Lyapunov exponents are numerically computed to confirm further the complexity of the dynamical behaviors. In addition, we show also the stabilizing effect of the harvesting by using numerical simulations. [ABSTRACT FROM AUTHOR]

In this article, a prey-predator system with Holling type II functional response for the predator population including prey refuge region has been analyzed. Also a harvesting effort has been considered for the predator population. The density-dependent mortality rate for the prey, predator and super predator has been considered. The equilibria of the proposed system have been determined. Local and global stabilities for the system have been discussed. We have used the analytic approach to derive the global asymptotic stabilities of the system. The maximal predator per capita consumption rate has been considered as a bifurcation parameter to evaluate Hopf bifurcation in the neighborhood of interior equilibrium point. Also, we have used fishing effort to harvest predator population of the system 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 is earned from the resource. Finally, we have presented some numerical simulations to verify the analytic results and the system has been analyzed through graphical illustrations. [ABSTRACT FROM AUTHOR]

SUMMARY We derive a closed-form solution for a well-known fisheries harvesting model with an additional state constraint. The problem is linear in the control and previous solutions appearing in the literature have been numerical in nature. The so-called direct adjoining approach is used in our derivation and the optimal solutions turn out to be a mixture of bang-bang and boundary arcs. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

An interactive web-based decision support system (DSS) was developed to assist the analysis of harvesting costs and productivity of roundwood operations in the Appalachian region. The DSS was designed using the ASP.NET platform via the VB.NET language and Microsoft (MS) SQL server. Three web pages were created: a main page for system configuration and simulation, a machine rate page for computing the handling machine costs requested by the main page, and a summary page for displaying all results. Stands, machines, and harvesting systems were modeled using previously published time and motion studies. An MS SQL server was used to retrieve the default information, to save the running results, and to populate the summary tables. A mathematical algorithm was designed to balance the harvesting system based on the machine productivity and use rates. The DSS was used to run three central Appalachian hardwood region-based simulations. The first simulation system was a chainsaw/cable skidder, the second was a feller-buncher/grapple skidder, and the final harvesting system used a harvester/forwarder. The simulation results were summarized including hourly machine rates and costs, system rate/cost, and the expected production rate for each harvesting system. The innovative DSS provides useful harvesting management decisionmaking information for loggers. [ABSTRACT FROM AUTHOR]