492 research outputs found

    Dynamics of a Double-Impulsive Control Model of Integrated Pest Management Using Perturbation Methods and Floquet Theory

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    We formulate an integrated pest management model to control natural pests of the crop through the periodic application of biopesticide and chemical pesticides. In a theoretical analysis of the system pest eradication, a periodic solution is found and established. All the system variables are proved to be bounded. Our main goal is then to ensure that pesticides are optimized, in terms of pesticide concentration and pesticide application frequency, and that the optimum combination of pesticides is found to provide the most benefit to the crop. By using Floquet theory and the small amplitude perturbation method, we prove that the pest eradication periodic solution is locally and globally stable. The acquired results establish a threshold time limit for the impulsive release of various controls as well as some valid theoretical conclusions for effective pest management. Furthermore, after a numerical comparison, we conclude that integrated pest management is more effective than single biological or chemical controls. Finally, we illustrate the analytical results through numerical simulations.Comment: This is a preprint of a paper whose final and definite form is published Open Access in 'Axioms' at [https://doi.org/10.3390/axioms12040391

    Application of Spread-Spectrum Ultrasonic Evaluation to Concrete Structures

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    Spread-Spectrum Ultrasonic Evaluation (SSUE) is an emerging technology for the global testing of structures and materials [1]. It incorporates the correlation properties of pseudo-random signals into ultrasonic NDE using spread-spectrum technology. The SSUE instrument records the ultrasonic correlation signature that is representation of the aggregate acoustic state of the test sample. The measured ultrasonic correlation signature is used for the detection of changes in the acoustic state of the test object. One major advantage of the SSUE technique is that it provides a global inspection of the material or structure without scanning. Some examples of unique SSUE applications are when; 1) the test object is of complex geometry or too large for scanning or, 2) the test material is a highly attenuative material such as concrete, wood, or composites. This paper reports the progress in applying the SSUE technique to concrete. The aim of the reported research is to study the propagation of the spread-spectrum signal in concrete structures of various sizes and determine the sensitivity of the SSUE correlation signature to changes in the various acoustic properties of the concrete object. A comparison of the SSUE technique with conventional ultrasonic NDE techniques for concrete testing is done and advantages of this technique for standard concrete inspection methods are discussed

    Estrous cycle influences excitatory amino acid transport and visceral pain sensitivity in the rat: Effects of early-life stress

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    Background: Early-life stress (ELS) is a recognized risk factor for chronic pain disorders, and females appear to be more sensitive to the negative effects of stress. Moreover, estrous cycle-related fluctuations in estrogen levels have been linked with alternating pain sensitivity. Aberrant central circuitry involving both the anterior cingulate cortex (ACC) and the lumbosacral spinal cord has also been implicated in the modulation of visceral pain in clinical and preclinical studies. Here we further investigate changes in visceral pain sensitivity and central glutamatergic systems in rats with respect to estrous cycle and ELS. Methods: We investigated visceral sensitivity in adult female Sprague-Dawley rats, which had undergone maternal separation (MS) in early life or remained non-separated (NS), by performing colorectal distension (CRD). We also assessed excitatory amino acid uptake through excitatory amino acid transporters (EAATs) in the lumbosacral spinal cord and ACC. Results: NS animals in proestrus and estrus exhibited reduced EAAT uptake and decreased threshold to CRD. Moreover, total pain behaviors were increased in these stages. MS rats exhibited lower pain thresholds and higher total pain behaviors to CRD across all stages of the estrous cycle. Interestingly, cortical EAAT function in MS rats was inhibited in the low estrogen state—an effect completely opposite to that seen in NS rats. Conclusions: This data confirms that estrous cycle and ELS are significant factors in visceral sensitivity and fluctuations in EAAT function may be a perpetuating factor mediating central sensitization

    Implementation of ANN Controller Based UPQC Integrated with Microgrid

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    This study discusses how to increase power quality by integrating a unified power quality conditioner (UPQC) with a grid-connected microgrid for clean and efficient power generation. An Artificial Neural Network (ANN) controller for a voltage source converter-based UPQC is proposed to minimize the system’s cost and complexity by eliminating mathematical operations such as a-b-c to d-q-0 translation and the need for costly controllers such as DSPs and FPGAs. In this study, nonlinear unbalanced loads and harmonic supply voltage are used to assess the performance of PV-battery-UPQC using an ANN-based controller. Problems with voltage, such as sag and swell, are also considered. This work uses an ANN control system trained with the Levenberg-Marquardt backpropagation technique to provide effective reference signals and maintain the required dc-link capacitor voltage. In MATLAB/Simulink software, simulations of PV-battery-UPQC employing SRF-based control and ANN-control approaches are performed. The findings revealed that the proposed approach performed better, as presented in this paper. Furthermore, the influence of synchronous reference frame (SRF) and ANN controller-based UPQC on supply currents and the dc-link capacitor voltage response is studied. To demonstrate the superiority of the suggested controller, a comparison of percent THD in load voltage and supply current utilizing SRF-based control and ANN control methods is shown

    Effective Ground-truthing of Supervised Machine Learning for Drone Classification

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    It has already been shown that multibeam staring radar is able to detect and track low observable targets such as drones due to its high sensitivity [1]. Due to this level of sensitivity, targets that have a similar RCS to drones are also detected and tracked. These are predominantly birds. Birds and drones are similar in several ways such as flight altitude, velocity and manoeuvrability [2] such that discrimination between them is challenging. Hence, there is a need to look for high performing methods of classification, for example, machine learning. Supervised training of machine learning classifiers requires accurately labelled training data. For control targets, such as drones, truth data from the on-board GPS logging can be used for data labelling. However, opportune bird targets require a separate data collection method that enables association with the radar output for a classifier to be effectively trained. This paper shows a method of collecting and displaying ground-truth for small targets onto GoogleEarth so that the radar data can be appropriately used to create accurate training data for a machine learning, drone and bird classifier. Results of classification performance are presented showing high performance that is aided by the availability of more effective truth data

    A Perspective on the Strategy for Advancing ETVAX®, An Anti-ETEC Diarrheal Disease Vaccine, into a Field Efficacy Trial in Gambian Children: Rationale, Challenges, Lessons Learned, and Future Directions.

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    For the first time in over 20 years, an Enterotoxigenic Escherichia coli (ETEC) vaccine candidate, ETVAX®, has advanced into a phase 2b field efficacy trial for children 6-18 months of age in a low-income country. ETVAX® is an inactivated whole cell vaccine that has gone through a series of clinical trials to provide a rationale for the design elements of the Phase 2b trial. This trial is now underway in The Gambia and will be a precursor to an upcoming pivotal phase 3 trial. To reach this point, numerous findings were brought together to define factors such as safe and immunogenic doses for children, and the possible benefit of a mucosal adjuvant, double mutant labile toxin (dmLT). Considering the promising but still underexplored potential of inactivated whole cells in oral vaccination, we present a perspective compiling key observations from past ETVAX® trials that informed The Gambian trial design. This report will update the trial's status and explore future directions for ETEC vaccine trials. Our aim is to provide not only an update on the most advanced ETEC vaccine candidate but also to offer insights beneficial for the development of other much-needed oral whole-cell vaccines against enteric and other pathogens

    A Grid-Connected Optimal Hybrid PV-BES System Sizing for Malaysian Commercial Buildings

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    In this article, the optimal sizing of hybrid solar photovoltaic and battery energy storage systems is evaluated with respect to rooftop space and feed-in tariff rates. The battery scheduling is performed using a proposed rule-based energy management strategy. The rules are formulated based on the demand limit, PV export power limit, and state of charge of the battery. Furthermore, optimization modeling with initial choices of parameters and constraints in terms of solar photovoltaic and battery energy storage capabilities is developed to minimize the total net present cost. The hourly values of solar irradiance, air temperature, electrical loads, and electricity rates are considered the inputs of the optimization process. The optimization results are achieved using particle swarm optimization and validated through an uncertainty analysis. It is observed that an optimal photovoltaic and battery energy storage system can reduce the cost of electricity by 12.33%,including the sale of 5944.029 kWh of electricity to the grid. Furthermore, energy consumption, peak demand, and greenhouse gas emissions are reduced by 13.71%, 5.85%, and 62.59%, respectively. A comprehensive analysis between the variable and fixed data for the load, energy from PV, batteries, and the grid, and costs demonstrates that the optimal sizing of photovoltaic and battery energy storage systems with the best mix of energy from PV, batteries, and the grid provides the optimal solution for the proposed configuration

    Time-optimal attitude control scheme for a spinning missile

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77165/1/AIAA-21009-332.pd

    Genetic Characterization of Nipah Virus, Bangladesh, 2004

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    Until 2004, identification of Nipah virus (NV)-like outbreaks in Bangladesh was based on serology. We describe the genetic characterization of a new strain of NV isolated during outbreaks in Bangladesh (NV-B) in 2004, which confirms that NV was the etiologic agent responsible for these outbreaks
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