Continuous Harvesting Research Articles

Complex dynamics of two prey–predator harvesting models with prey refuge and interval‐valued imprecise parameters

In view of the phenomena that species in nature are affected by the complexity of the ecosystem, some key biological parameters have certain inaccuracy or uncertainty and part of the prey hides in the shelter from predation. Moreover, different species exhibit different living habits, so it is of certain interest to investigate species‐related imprecise biological parameters. Besides, from the perspective of scientific and reasonable exploitation and utilization of fishery resources, two types of harvesting strategies are introduced into the system. Firstly, the dynamic properties of the system guided by continuous harvesting strategy are analyzed, which demonstrates the impact of refuge rate, imprecision indexes and harvesting efforts on the system dynamics. Meanwhile, the bio‐economic equilibrium is discussed, and the optimal harvesting strategy is obtained. Secondly, the complex dynamics of the system induced by weighted harvesting activity are analyzed. The predator‐extinction periodic solution and coexistent order‐1 periodic solution is discussed according to different weights and thresholds. Finally, the correctness of the obtained results and the feasibility of the harvesting strategy are verified through numerical simulation in MATLAB. The results of this study provide a reference for the scientific and reasonable exploitation and utilization of prey–predator fishery resources in the imprecise parameter environment.

DENSITY AND DISTRIBUTION PATTERNS OF FULL-BLOODED CLAM (GELOINA EXPANSA; MOUSSON, 1849) IN MANGROVE ECOSYSTEMS

Geloina expansa is a clam found in mangrove forests. The high level of public consumption and high economic value, is suspected as the cause of overfishing. It is not impossible that continuous harvesting will result in a decrease in the population of G. expansa. The habitat of G. expansa has experienced a lot of land conversion and this will result in a decrease in the natural carrying capacity of its habitat. The purpose of this study was to determine the distribution and density, distribution pattern and size distribution of the population of G. expansa based on the ecology of its habitat in West Malangke waters. The method was carried out randomly, the transect was placed in a 5x5 m2 sample plot with 3 replications and collected directly by hand. Sampling was carried out on each plot at the lowest ebb. Environmental parameters measured in the field included salinity, temperature and substrate while parameters measured in the laboratory were total organic matter (TOM). The density value of G. expansa in the intertidal zone was 9.90 ind/m2 while in the subtidal zone it was 0.78 ind/m2. The distribution pattern found in the intertidal and subtidal zones is clustered. The size distribution of G. expansa in the intertidal zone found that the dominant G. expansa was adult size, and the lowest was in the old size class while in the subtidal zone the dominant size was young and the lowest was in the old size class. Zone and type of substrate affect the existence of G. expansa. G. expansa was found more in the intertidal zone than in the subtidal zone and clay-type of substrates were a determining factor for the presence of full-blooded clams while clay and sand-type substrates were limiting factors for the presence of full-blooded clams.

MXene and Carbon-Based Electrodes of Thermocells for Continuous Thermal Energy Harvest.

Low-grade heat represents a significant form of energy loss; thermocells (TECs) utilizing the thermogalvanic effect can convert thermal energy into electricity without generating vibrations, noise, or waste emissions, making them a promising energy conversion technology for efficiently harvesting low-grade heat. Despite recent advancements, the reliance on high-cost platinum electrodes in TECs has considerably hindered their widespread adoption. Developing cost-effective electrodes that maintain the same thermoelectrochemical performance is crucial for the successful application of TECs. In this review article, the exploration of MXene materials as TEC electrodes is discussed first, emphasizing the immense potential of the MXene family for low-grade heat harvesting applications. Next, recent research on carbon-based electrodes is summarized, and morphological and structural optimizations are comprehensively discussed aiming at enhancing the thermoelectrochemical performance of TECs. In the concluding section, the challenges are outlined and future perspectives are offered, which provide valuable insights into the ongoing development of high-performance TEC electrodes using MXene and carbon-based materials.

Bacterial cellulose hydrogel-based wearable thermo-electrochemical cells for continuous body heat harvest

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Experimental studies from shake flasks to 3 L stirred tank bioreactor of nutrients and oxygen supply conditions to improve the growth of the avian cell line DuckCelt®-T17

BackgroundTo produce viral vaccines, avian cell lines are interesting alternatives to replace the egg-derived processes for viruses that do not grow well on mammalian cells. The avian suspension cell line DuckCelt®-T17 was previously studied and investigated to produce a live attenuated metapneumovirus (hMPV)/respiratory syncytial virus (RSV) and influenza virus vaccines. However, a better understanding of its culture process is necessary for an efficient production of viral particles in bioreactors.ResultsThe growth and metabolic requirements of the avian cell line DuckCelt®-T17 were investigated to improve its cultivation parameters. Several nutrient supplementation strategies were studied in shake flasks highlighting the interest of (i) replacing L-glutamine by glutamax as main nutrient or (ii) adding these two nutrients in the serum-free growth medium in a fed-batch strategy. The scale-up in a 3 L bioreactor was successful for these types of strategies confirming their efficiencies in improving the cells’ growth and viability. Moreover, a perfusion feasibility test allowed to achieve up to ~ 3 times the maximum number of viable cells obtained with the batch or fed-batch strategies. Finally, a strong oxygen supply – 50% dO2 – had a deleterious effect on DuckCelt®-T17 viability, certainly because of the greater hydrodynamic stress imposed.ConclusionsThe culture process using glutamax supplementation with a batch or a fed-batch strategy was successfully scaled-up to 3 L bioreactor. In addition, perfusion appeared as a very promising culture process for subsequent continuous virus harvesting.

Deep learning-based energy harvesting with intelligent deployment of RIS-assisted UAV-CFmMIMOs

The ever-evolving internet of things (IoT) has spawned hundreds of wireless sensors that communicate via the internet infrastructure. The lifetime and self-sustainability of these sensors are pivotal factors dictating the performance of respective application infrastructure. Radio frequency energy harvesting (RFEH) technology has exhibited the capability of effectively augmenting the battery lifetime of these sensors. In this work, we introduce a novel framework called CURe, which combines the advantages of cell-free massive multiple-input multiple-output (CFmMIMO) and reconfigurable intelligent surfaces (RISs) to provide uninterrupted energy harvesting for IoT devices through RFEH. CFmMIMO integrates the advantages of distributed systems and massive MIMO, while RIS improves the signal strength of the information transfer and RFEH via its passive reflection capabilities. Moreover, we consider unmanned aerial vehicles (UAVs) equipped with CFmMIMO as mobile access points (APs) to better serve the moving sensory devices. To further enhance RFEH, we propose DeNCE, a channel estimation technique based on deep learning (DL) that eliminates the need for traditional closed-form equation-based channel estimation methods. Through evaluation, we first validate the performance of CURe by comparing it with the modified bisection search for max–min fairness (MBS-MMF) algorithm and later corroborate that DeNCE significantly improves the performances of both models. Finally, to optimize the UAV deployment and ensure continuous RFEH coverage, we propose dARL, a deep reinforcement learning (DRL)-based scheduling framework that enables UAV-CFmMIMO swarms to perform continuous energy harvesting in the coverage area collaboratively.

Three-dimensional ordered macroporous molybdenum doped NiCoP honeycomb electrode for two-step water electrolysis

Two-step alkaline water electrolysis is considered a safe and efficient method for producing hydrogen from renewable energy. Reversal of the current polarity in a bifunctional electrocatalyst used as a gas evolution electrode (GEE) in two-step water electrolysis can generate H2/O2 at different times and in different spaces. The design of a bifunctional electrocatalyst with high durability and excellent activity is imperative to achieving continuous, safe, and pure H2 generation via two-step alkaline water electrolysis. Here, we present for the first time a novel 3D Mo-doped NiCo phosphide honeycomb electrocatalyst that was grown on nickel foam (3D Mo-NiCoP/NF) and fabricated using polystyrene as a template. The electrocatalyst exhibited extremely low overpotentials in both the hydrogen evolution reaction (HER; 117 mV at 10 mA/cm2) and the oxygen evolution reaction (OER; 344 mV at 100 mA/cm2). As a bifunctional electrocatalyst for two-step alkaline water electrolysis, the device had a 1.784 V cell voltage at 10 mA/cm2, 95% decoupling efficiency, and ∼83% energy conversion efficiency. Taken together, the use of 3D Mo-NiCoP/NF as a GEE reduced the complexity and lowered the cost of the electrolyzer. The latter could be used to construct highly competitive water-splitting systems for continuous H2 production and green energy harvesting.

Dynamic analysis of a stage-structured forest population model with non-smooth continuous threshold harvesting

In this article, we develop a delayed tree population model with non-smooth continuous threshold harvesting. By carefully addressing the main difficulty caused by the nonlinear term and the time delay together, the existence and number of the positive equilibrium points are classified. Taking full use of the domain-decomposition method and Hopf bifurcation theory, the stability of the model, including local and global asymptotic stability of the equilibria, bistability and stability switches occurring at the positive equilibrium, is analyzed relatively completely. This is followed by an investigation of the influence of the maturation delay of trees on the optimal harvesting. Numerical analysis illustrates that the model gives rise to chaotic-like oscillations through period doubling with the increase of the maturation delay or the harvesting rate and undergoes long transients and regime shifts. Even, the maturation delay can induce multi-types of tristability.

Process intensification strategies towardcell culture-based high-yield production of a fusogenic oncolytic virus.

We present a proof-of-concept study for production of a recombinant vesicular stomatitis virus (rVSV)-based fusogenic oncolytic virus (OV), rVSV-Newcastle disease virus(NDV), at high cell densities (HCD). Based on comprehensive experiments in 1 L stirred tank reactors (STRs) in batch mode, first optimization studies at HCD were carried out in semi-perfusion in small-scale cultivations using shake flasks. Further, a perfusion process was established using an acoustic settler for cell retention. Growth, production yields, and process-related impurities were evaluated for three candidate cell lines (AGE1.CR, BHK-21, HEK293SF)infected at densities ranging from 15 to 30 × 106 cells/mL. The acoustic settler allowed continuous harvesting of rVSV-NDV with high cell retention efficiencies (above 97%) and infectious virus titers (up to 2.4 × 109 TCID50 /mL), more than 4-100 times higher than for optimized batch processes. No decrease in cell-specific virus yield (CSVY) was observed at HCD, regardless of the cell substrate. Taking into account the accumulated number of virions both from the harvest and bioreactor, a 15-30 fold increased volumetric virus productivity for AGE1.CRand HEK293SF was obtained compared to batch processes performed at the same scale. In contrast to all previous findings, formation of syncytia was observed at HCD for the suspension cells BHK 21 and HEK293SF. Oncolytic potency was not affected compared to production in batch mode. Overall, our study describes promising options for the establishment of perfusion processes for efficient large-scale manufacturing of fusogenic rVSV-NDV at HCD for all three candidate cell lines.

Aqueous biphase-boosted liquid-state thermocell for continuous low-grade heat harvesting

Low-grade heat (<100 °C) is widespread and vast potential source of power to be exploited. Liquid-state thermocell (LTC) has provided an alternative approach to directly convert low-grade heat into electricity to help carbon emission reduction. Seebeck coefficient (Se), electrical conductivity (σ) and thermal conductivity (κ) are the three interdependent key factors determining the performance of LTCs. However, most of the previous researches focused on improving Se and σ while ignoring the factor κ. Here, we introduce an aqueous biphasic system as solvent to fabricate electrolytes for LTCs. The aqueous biphasic electrolytes can not only offer different solvation environment near the electrodes, but also suppress the thermal convection, hence result in improved Se and reduced κ. With the aqueous biphasic electrolyte of K3Fe(CN)6/K4Fe(CN)6 as the redox couple, the Se of the LTC was doubled and the output power was improved over 5 times. Furthermore, with the help of porous graphite felt as electrode material, the output power can be improved over 7 times. This work provides a new pathway for the development of high-performance LTC to harvest low-grade heats.

Temporal and Spatial Distribution, Utilization Status, and Carbon Emission Reduction Potential of Straw Resources in China

Temporal and Spatial Distribution, Utilization Status, and Carbon Emission Reduction Potential of Straw Resources in China

Continuous Threshold Harvesting Intermediate Predator in Food Chain Model

This paper presents a three-species food chain system, which consists of intermediate predator population that depends only on prey population, and top predator population that depends only on intermediate predator population. We study this model when the intermediate predator exposed to the risk of harvest.&#x0D; We studied the bounded solutions and equilibrium points with its conditions. Also the stability for each equilibrium points was studied. We determine the invariant region, in this region all population are survive and continuous harvesting. At last, we describe some results in numerical simulation

A predator-prey model for the optimal control of fish harvesting through the imposition of a tax

This paper is devoted to the study of ecosystem based fisheries management. The model represents the interaction between prey and predator population with Holling II functional response consisting of different carrying capacities and constant intrinsic growth rates. We have considered the continuous harvesting of predator only. It is observed that if the intrinsic growth rate of predator population crosses a certain critical value, the system enters into Hopf bifurcation. Our observations indicate that tax, the management object in fisheries system play huge impacts on this system. The optimal harvesting policy is disposed by imposing a tax per unit of predator biomass. The optimal harvest strategy is determined using Pontryagin's maximum principle, which is subject to state equations and control limitations. The implications of tax are also examined. We have derived different bifurcations and global stability of the system. Finally, numerical simulations are used to back up the analytical results.

Periodic dynamics of a single species model with seasonal Michaelis-Menten type harvesting

In this paper, we formulate a seasonally interactive model between closed seasons and open seasons with Michaelis-Menten type harvesting based on some management and capture methods of renewable resources. It is assumed that the population growth obeys the logistic equation in closed seasons and is captured following Michaelis-Menten type response function in open seasons. We define a length threshold of the closed season T¯⁎, which depends on the harvesting parameter. Under the extinct condition of the corresponding continuous harvesting model, by setting the closed season, theoretical results show that the origin is globally asymptotically stable if and only if T¯≤T¯⁎, and there exists a unique globally asymptotically stable T-periodic solution if and only if T¯>T¯⁎. In particular, under the critical conditions on special harvest parameters, it is found that the T-periodic solution still exists as long as an arbitrary positive close season is formulated. Numerical examples are carried out to confirm the obtained theoretical results. Brief conclusions and discussions on our findings are also provided.

Aboveground carbon sequestration rate in alpine forests on the eastern Tibetan Plateau: impacts of future forest management options

AbstractAlpine forests in the eastern Tibetan Plateau are important ecological barriers in the upper reaches of the Yangtze River. However, due to continuous high-intensity harvesting, a large number of plantings, and the complete harvesting ban measures in recent decades, the forest tree species and age cohorts have become relatively homogenous, and the biodiversity and ecological functions have been reduced. To design effective forest management options to optimize forest structure and increase carbon sequestration capacity, Mao County in Sichuan Province was selected as the study site and six forest management options (harvesting, planting) of different intensities were tested using the LANDIS-II model to simulate and compare the differences in forest aboveground carbon sequestration rate (ACSR) between these options and the current management option over the next 100 years. Our results showed that (i) the different harvesting and planting intensities significantly changed the ACSR compared with the current management options; (ii) different communities responded differently to the management options, with the ACSR differing significantly in cold temperate conifers and temperate conifers but not in broad-leaved trees (P &amp;lt; 0.05); and (iii) a comprehensive consideration of forest management options at the species, community and landscape levels was necessary. Our results suggest that implementing a longer harvesting and planting interval (20 years) at the study site can maximize forest ACSR. This study provides an important reference for evaluating the ability of forest management options to restore forest ecological functions and increase carbon sequestration capacity and for selecting effective forest management programs in the eastern Tibetan Plateau.

Complex dynamics and optimal harvesting strategy of competitive harvesting models with interval-valued imprecise parameters

Considering that species in nature are affected by the complexity of the ecosystem, biological parameters present certain inaccuracy or uncertainty. Different species exhibit different living habits, so it is of certain interest to investigate species related imprecise parameters. Besides, from the perspective of scientific and reasonable exploitation and utilization of fishery resources, two types of two-species competitive models with species related interval-valued imprecise parameters and harvesting are established. Firstly, the influence of interval-valued imprecise parameters on the dynamic behavior of the system without harvest are analyzed. Then, for continuous harvesting system, the existence of bio-economic equilibrium is discussed, and the optimal harvesting strategy is obtained by using Pontryagin’s maximum principle. Next, for the system guided by weighted harvesting strategy, the existence and stability of the order-1 periodic solution are discussed. Besides, in order to find the harvesting strategy that maximizes the economic profit in the harvest process, an optimization problem is constructed according to the actual situation, and the optimal set values of the weight and threshold of the strategy are obtained. Finally, the correctness of the obtained results and the feasibility of the harvesting strategy are verified through numerical simulation in MATLAB. The results of this study provide a reference for the scientific and reasonable exploitation and utilization of competitive fishery resources in the imprecise parameter environment.

Efeito do espaçamento e corte no desenvolvimento de guandu sob condições subtropicais

ABSTRACT Depending on the purpose of its cultivation, pigeon pea can be grown under different spacings and cuts, since it quickly resprouts. This study aimed to assess the pigeon pea growth, forage production and quality, considering two spacings and one cut. A field experiment using a completely randomized design, with three treatments [1.0 × 0.2 m spacing (between rows and plants, respectively), without cuts; 0.5 × 0.1 m, without cuts; and 0.5 × 0.1 m, with cut at 90 days after emergence (DAE)], was carried out. The spacings did not affect the plant height. The 0.5 × 0.1 m spacing showed an individual plant growth worse, but a forage yield (kg ha-1) higher than the 1.0 × 0.2 m treatment, from 120 to 180 DAE. The 0.5 × 0.1 m spacing was more advantageous than the 1.0 × 0.2 m, with the highest forage yield obtained by harvesting at 150 DAE. It is better to harvest the forage at 90 DAE and harvest it again at 180 DAE than maintaining a continuous plant growth and harvest it at 180 DAE. In each sampling date, there was no difference for stem and leaf crude protein and starch content as a function of the treatments. The forage harvested from 90 to 180 DAE showed similar crude protein and starch contents. So, for this period, the forage quality is not a limiting factor for establishing the harvest time.

Predictive analysis of smart agriculture using IoT-based UAV and propagation models of machine learning

Every year, unfavourable weather conditions cause many crops to fail. Every time, over 12 million dollar losses are recorded. This article provides a proper background for delivering the yield's current state. The project proposes to employ IoT-based unmanned aerial vehicles (UAVs) and tensor-flow machine learning to estimate crop yields. This framework enhances agricultural yield accuracy by using UAVs. The IoT-enabled UAV module captures data and texts it to the farmer or rancher. The data cloud storage's server uses MQTT for safe data transmission. The cloud server leverages UAV for continuous surveillance and harvest forecasts. Predictive analysis using propagation model has an accuracy of roughly 85% compared to real-time analysis for the same crops at the farm.

Solar-thermo-radiative evaporator for continuous steam generation and salt harvesting

Solar-driven interfacial evaporation attracts great attention in desalination and wastewater treatment. However, the gradual decline of evaporation rate caused by salt accumulation restricts its long-term operation. Here, we developed a new solar-thermo-radiative evaporator that uses infrared photons as heating source to promote the interfacial evaporation with edge-preferential crystallization and gravity-assisted salt harvesting. The solar absorber exhibits broadband light-harvesting and converts the sunlight into mid-infrared radiation, localizing the radiative heat at the neighboring water-film for directly phase-change evaporation. Benefiting from the self-manipulated salt water transport, this evaporator spatially isolates the crystallized salts from the evaporative surface, achieving an evaporation rate (0.71 kg∙m−2∙h−1) with high steam temperature (＞80 °C) under 1 sun. As the salt is continuously expelled at the edge of the evaporator, the salt-harvesting performance (36.25 g∙m−2∙h−1) is achieved during 40 h of non-stop solar desalination without affecting water evaporation. Such non-contact design thus circumvents the salt-blocking and/or contamination issue on the solar absorber, making it uniquely suitable for applications in desalination or water purification, with an added benefit of resources recovery.

Green synthesis of silver nanoparticles from peel extract of Chrysophyllum albidum fruit and their antimicrobial synergistic potentials and biofilm inhibition properties.

Current methods for green synthesis of metal nanoparticles often require continuous harvesting of fresh bio-materials for every synthesis cycle. Practices and procedures that economize bio-materials need to be employed if green synthesis could become a sustainable and eco-friendly method for synthesizing metal nanoparticles. This study explores Chrysophyllum albidum peels (mostly regarded as waste) to prepare silver nanoparticles (Alb-AgNPs). The technique employed in the synthesis allows repeated use of the peels, thus, reducing the heavy dependence on bio-materials. The optical and structural properties of the Alb-AgNPs were studied with Scanning electron microscope, Fourier transform infrared spectrometer, UV-Vis spectrophotometer and powder X-ray diffractometer. The antimicrobial properties of the Alb-AgNPs were studied with selected microorganisms namely; S. aureus, E. coli, K. pneumoniae, B. subtilis, S. mutans, P. aeruginosa, S. typhi, and Candida albicans. High inhibitory activity against the microorganisms were exhibited with MICs ranging from 15.62 to 1000µg/mL. Again, the Alb-AgNPs showed the ability to enhance the efficacy of standard antimicrobial agents. The results of the combined interaction with standard antibacterial and antifungal agents ranged from synergistic to antagonistic effects against the tested microorganisms. In addition, the Alb-AgNPs could serve as a biofilm inhibitor with the highest percent inhibition of about 92% against methicillin-resistant Staphylococcus aureus. The results from this study thus provide access to the simple, sustainable, economic and eco-friendly synthesis of silver nanoparticles with efficient antimicrobial properties as drug candidates as a means of overcoming the prevailing antibiotic resistance menaces.