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Author(s):  
Yuqi Pang ◽  
Gang Ma ◽  
Xiaotian Xu ◽  
Xunyu Liu ◽  
Xinyuan Zhang

Background: Fast and reliable fault detection methods are the main technical challenges faced by photovoltaic grid-connected systems through modular multilevel converters (MMC) during the development. Objective: Existing fault detection methods have many problems, such as the inability of non-linear elements to form accurate analytical expressions, the difficulty of setting protection thresholds and the long detection time. Method: Aiming at the problems above, this paper proposes a rapid fault detection method for photovoltaic grid-connected systems based on Recurrent Neural Network (RNN). Results: The phase-to-mode transformation is used to extract the fault feature quantity to get the RNN input data. The hidden layer unit of the RNN is trained through a large amount of simulation data, and the opening instruction is given to the DC circuit breaker. Conclusion: The simulation verification results show that the proposed fault detection method has the advantage of faster detection speed without difficulties in setting and complicated calculation.


2021 ◽  
Author(s):  
Ellen A Kearney ◽  
Paul A Agius ◽  
Victor Chaumeau ◽  
Julia C Cutts ◽  
Julie A Simpson ◽  
...  

Background: Entomological surveillance for malaria is inherently resource-intensive and produces crude population-level measures of vector exposure which are insensitive in low-transmission settings. Antibodies against Anopheles salivary proteins measured at the individual-level may serve as proxy biomarkers for vector exposure and malaria transmission, but their relationship is yet to be quantified. Methods: A systematic review of studies measuring antibodies against Anopheles salivary antigens (PROSPERO: CRD42020185449). Multilevel modelling estimated associations between seroprevalence with Anopheles human biting rate (HBR) and malaria transmission measures.Results: From 3981 studies identified in literature searches, 42 studies across 16 countries were included contributing 393 meta-observations of anti-Anopheles salivary antibodies determined in 42,764 samples. A positive non-linear association between HBR and seroprevalence was found; overall a 50% increase in HBR was associated with a 13% increase in odds of seropositivity (OR: 1.13, 95%CI: 1.06-1.20, p<0.001). The association between HBR and Anopheles salivary antibodies was strongest with concordant, rather than discordant Anopheles species. Seroprevalence was also significantly positively associated with established epidemiological measures of malaria transmission: entomological inoculation rate, Plasmodium spp. prevalence, and malarial endemicity class.Conclusions: Anopheles salivary antibody biomarkers can serve as a proxy measure for HBR and malaria transmission, and could monitor vectorial capacity and malaria receptivity of a population to sustain malaria transmission. Validation of Anopheles species-specific biomarkers are important given the global heterogeneity in the distribution of Anopheles species. Salivary biomarkers have the potential to transform surveillance by replacing impractical, inaccurate entomological investigations, especially in areas progressing towards malaria elimination.Funding: Australian National Health and Medical Research Council, Wellcome Trust.


2021 ◽  
Author(s):  
N.H. Abdel-Wahab ◽  
S. Abdel-Khalek ◽  
E.M. Khalil ◽  
Nawal Alshehri

Abstract The aim of this paper is to study the interaction between a single mode field and four-level atom in N - configuration under nonlinear medium effect. The non-resonance case and the deformation forms in the coupling interaction between the field and the atom are included. The wave function of the proposed system is obtained when the atom is prepared initially in its excited state while the field is prepared in a coherent state. The effect of the deformation and nonlinear medium on the temporal behavior of collapse-revival, field entropy and geometric phase of the system are examined. The results show that the presence of the intensity of the coupling interaction and the non-linear medium have an important influence on the properties of these phenomena.


2021 ◽  
pp. 263497952110427
Author(s):  
Leniqueca A Welcome ◽  
Deborah A Thomas

The recent renewal of attention to abstraction within Black literary and visual studies, it seems to us, has to do with an interest in the various ways abstraction rejects ascribed categories, eschews narrow assumptions about “relevance,” and embraces experimentation during a moment when it is arguably most needed. Abstraction moves us simultaneously outside of representative realism, and it embraces research practices that often require the kind of intimacies that have long been the bread and butter of anthropology. As multimodal ethnographers, we have long made our ethical commitments to interlocutors through embodied participation and collective knowledge production. In this essay, we attend to questions of abstraction, witnessing, and refusal within our own filmic and photographic practices addressing state violence in the Caribbean. We are interested in the spatio-temporality of both witnessing and refusal and in the relationships between form and audience. We are interested in how forms of abstraction capture the ephemeral, performative, affective, non-linear, and unpredictable ways something that feels like sovereignty circulates and is transmitted from one to another, without contributing to a process of overexposure or a desire for transparency.


2021 ◽  
Author(s):  
Logan A. Sauers ◽  
Kelsey E. Hawes ◽  
Steven A. Juliano

Abstract Understanding the relationship of population dynamics to density is central to many ecological investigations. Despite the importance of density-dependence in determining population growth, the empirical relationship between density and per capita growth remains understudied in most systems and is often assumed to be linear. In experimental studies of interspecific competition, investigators often evaluate the predicted outcomes by assuming such linear relationships, fitting linear functions, and estimating parameters of competition models. In this paper, we tested experimentally the shape of the relationship between estimated population rate of change and initial density using laboratory-reared populations of three mosquito species. We estimated per capita growth rate for these experimental populations over a thirty-fold range of larval densities at a standard resource abundance. We then compared fits of linear models and several different nonlinear models for the relationship of estimated rate of change and density. We find that that the relationship between density and per capita growth is strongly non-linear in all three mosquitoes. Components of population growth (survivorship, development time, adult size) are also nonlinearly related to initial density. The causes and consequences of this nonlinearity are likely to be important issues for population and community ecology.


2021 ◽  
Vol 9 ◽  
Author(s):  
Qingyi Luo ◽  
Ming-Chih Chiu ◽  
Lu Tan ◽  
Qinghua Cai

A suitable environmental flow is critical for the functional maintenance of riverine ecosystems. Hydropower plants alter the flow regime by decreasing or even drying up the streamflow downstream of the dams, thereby affecting ecosystem sustainability. In this study, we aimed to develop a robust environmental flow framework that can provide scientific evidence for sustainable water resource management. Using ecological niche modeling based on non-linear responses of species to habitat factors, we assessed the environmental flow in the Xiangxi River Basin of Central China during dry and wet seasons from a multi-year perspective. The most abundant macroinvertebrate taxon (i.e., Baetis) was selected for model testing. The results showed seasonal differences in the minimum ecological water requirements and optimal environmental flow. These two hydrological metrics were higher during the wet season than during the dry season. During the dry season, the minimum ecological water requirement of Baetis was 1.3 m3·s−1, and the optimal environmental flow was 1.6 m3·s−1. During the wet season, the minimum ecological water requirement of Baetis was 2.5 m3·s−1, and the optimal environmental flow was 2.6 m3·s−1. This study provides a theoretical basis for the robust management of water resources in river basins.


Author(s):  
J. D. González-San Román ◽  
J. U. Liceaga-Castro ◽  
I. I. Siller-Alcalá ◽  
E. Campero-Littlewood

This work presents the process of obtaining the simplified model of a switched reluctance motor (SRM) 8/6. Subsequently, the structure of the single-phase model is analyzed, obtaining an exact linearization and zero dynamics of the system. Finally, the model is linearized at an operating point set at 2000 rpm The model includes Coulomb plus viscous friction nonlinearity and an ideal inverter circuit based on bridge converter topology. The simplified and linear models are simulated and compared in the Matlab®/Simulink software in order to validate the design of a classic controller using the linear model.


2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Martin Kretschmer ◽  
Benjamin Winkeljann ◽  
Brigitte A. K. Kriebisch ◽  
Job Boekhoven ◽  
Oliver Lieleg

AbstractAbout ten years ago, chemically fueled systems have emerged as a new class of synthetic materials with tunable properties. Yet, applications of these materials are still scarce. In part, this is due to an incomplete characterization of the viscoelastic properties of those materials, which has – so far – mostly been limited to assessing their linear response under shear load. Here, we fill some of these gaps by comparing the viscoelastic behavior of two different, carbodiimide fueled Fmoc-peptide systems. We find that both, the linear and non-linear response of the hydrogels formed by those Fmoc-peptides depends on the amount of fuel driving the self-assembly process – but hardly on the direction of force application. In addition, we identify the concentration of accumulated waste products as a novel, so far neglected parameter that crucially affects the behavior of such chemically fueled hydrogels. With the mechanistic insights gained here, it should be possible to engineer a new generation of dynamic hydrogels with finely tunable material properties that can be tailored precisely for such applications, where they are challenged by mechanical forces.


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