Circuit Theory Approach Research Articles

Integrating high-resolution remote sensing and empirical wildlife detection data for climate-resilient corridors across tropical elevational gradients

Corridors are essential tools for promoting biodiversity resilience under climate change. However, corridor design studies are often conducted at spatial scales too coarse to guide implementation by local conservation practitioners. We mapped potential climate-resilient corridors linking lowland to highland protected areas within a highly biodiverse but fragmented landscape of southwestern Costa Rica (6311 km2) using least cost path and circuit theory approaches at high spatial resolution (10 m). We then applied an extensive camera trap dataset of medium-large vertebrates to examine corridor functionality. Although least cost paths (n = 40) were predominantly forested (median = 76 %, range = 57–82 %) and somewhat protected (median = 31 %, range = 3–55 %), they were also highly fragmented. Least cost paths from lowland to highland protected areas traversed medians of 252 forest patches (range = 162–328), 11,186 agriculture patches (range = 822–1,771), and 106 roads (range = 50–252), translating to 2 forest patches, 11 agriculture patches, and 1 road crossed every kilometer. Circuit analyses identified many high-connectivity areas outside of protected areas, including but not limited to least cost paths, but these high-connectivity areas were mostly small forest fragments. Nonetheless, capture rates for medium-to-large mammals at camera traps indicated that many species are currently unlikely to use unprotected, fragmented areas thought to be important for connectivity. In other words, additional conservation and restoration are necessary to establish functional corridors within the landscape. More broadly, this study exemplifies an approach to bridging the gap between regional-scale connectivity analyses and the needs of local practitioners by identifying locations that could be targeted for conservation or restoration within multi-use tropical landscapes.

On the elephant trails: habitat suitability and connectivity for Asian elephants in eastern Indian landscape.

Identifying suitable habitats and conserving corridors are crucial to the long-term conservation of large and conflict-prone animals. Being a flagship species, survival of Asian elephants is threatened by human-induced mortality and habitat modification. We aimed to assess the habitat suitability and connectivity of the Asian elephant Elephas maximus Linnaeus, 1758 habitat in the state of Odisha in eastern India. We followed the ensemble of spatial prediction models using species presence data and five environmental variables. We used least-cost path and circuit theory approaches to identify the spatial connectivity between core habitats for Asian elephants. The results revealed that normalized difference vegetation index (NDVI; variable importance 42%) and terrain ruggedness (19%) are the most influential variables for predicting habitat suitability of species within the study area. Our habitat suitability map estimated 14.6% of Odisha's geographical area (c. 22,442 km2) as highly suitable and 13.3% (c. 20,464 km2) as moderate highly suitable. We identified 58 potential linkages to maintain the habitat connectivity across study area. Furthermore, we identified pinch points, bottlenecks, and high centrality links between core habitats. Our study offers management implications for long-term landscape conservation for Asian elephants in Odisha and highlights priority zones that can help maintain spatial links between elephant habitats.

Analysis of grounding system transient with consideration of soil ionization and mutual coupling effect

The grounding system of an electrical substation provides safety to both operator and equipment. The lightning current waveform has a major influence on the dynamic performance of ground electrodes. If lightning current is large enough, soil will be ionized, which will have a great effect on the transient performance of the grounding system. Many numerical models have been developed to evaluate the transient performance of grounding system, still it is a challenging task to analyze the impulse behavior of grounding system efficiently. In this paper, the transient behavior of grounding systems with consideration of nonlinear and dynamic effects of soil ionization is presented. Grounding systems such as vertical rod, horizontal conductor and grounding grid buried in the homogeneous soil are considered as case study. Proposed model is the combination of circuit theory approach and method of moment with consideration of frequency-dependent impedance and mutual coupling effect between the conductor segments. Self and mutual component of inductance and resistance are considered in the analysis. Initially, transient performance of grounding system is analyzed for single vertical rod, horizontal and square grounding electrodes, further it is extended for vertical rod (more than one), horizontal conductor and grounding grids with different configurations. The analysis of grounding system with the consideration of mutual coupling effect is compared with devoid of mutual coupling, and differences between them are evaluated. For validating the developed method, simulated results are compared with the results reported in the literature, and good agreements are found. Analysis shows that the grounding impulse impedance decreased with increasing the magnitude of injected current. Developed method will help to improve the modeling of simple as well as complex grounding system buried in homogeneous soil.

Construction of ecological network based on habitat risks identifying by points of interest: A case study of Wuhan Metropolitan Area.

Ecological network construction plays a key role in ecological restoration, which can effectively mitigate negative effects of habitat fragmentation on biodiversity. Here, we proposed an improved analytical framework for ecological network identification. Specifically, ecological sources were identified using a three-dimension indicator system in terms of form, quality and functions of habitats. Ecological resistance surfaces were determined based on the incorporation of points of interest data that could characterize human activities into habitat risk assessment (HRA) model, while ecological corridors were extracted using circuit theory approach. With Wuhan Metropolitan Area as a case, we explored the key points and structures of ecological network. Moreover, we compared the construction method of ecological resistance surface based on points of interest and HRA model with traditional methods that determined by land use types and by traditional HRA model, to validate the proposed framework. The results showed that the ecological source area of Wuhan Metropolitan Area was 15200 km2, the length of ecological corridor was 1956.68 km, and that there were 87 ecological "pinch points" and 67 ecological barrier points. Compared with traditional methods, the material circulation, network complexity, and ecological connectivity of the ecological network identified by the improved framework were significantly improved, with network closure, dot-line ratio, and network connectivity being increased by 61.5%, 28.1% and 28.7% on average. The identified ecological "pinch points" and barrier points could provide precise decision-making support for ecological restoration and conservation.

Uncovering Gas Insulated Substation Transient Behaviours Using the Equivalent Cable Model

An improved circuit theory approach is proposed for verification of data obtained with the Electro-Magnetic Field (EMF) theory for the study of Gas Insulated Substations (GIS) transient behaviours. The improved circuit theory utilises the concept of an equivalent cable model. The proposed equivalent cable model reduces time and eliminates costs associated with experimentation, which in some cases is not feasible. Also reported is the degree of accuracy in using the proposed model as a benchmark for verification purposes.

Electrical Circuits Simulator in Null-Flux Electrodynamic Suspension Analysis

This paper employed an electrical circuit simulator to investigate an electrodynamic suspension system (EDS) for passenger rail transport applications. Focusing on a null-flux suspension system utilizing figure-eight-shaped coils (8-shaped coils), the aim was to characterize the three primary electromagnetic forces generated in an EDS and to compare the findings with existing literatures. The dynamic circuit theory (DCT) approach was utilized to model the system as an electrical circuit with lumped parameters, and mutual inductance values between the superconducting (SC) coil and the upper and lower loops of the 8-shaped coil were calculated and inputted into the simulator. The results were compared with experimental data obtained from the Yamanashi test track. The comparison demonstrated close alignment between the theoretical expectations and the obtained experimental curves, validating the accuracy of the proposed model. The study highlights the advantages of this new approach, including faster computation times and efficient implementation of modifications. Overall, this work contributes to the ongoing development and optimization of null-flux suspension Maglev systems.

Does scale or method matter for conservation? Application of directional and omnidirectional connectivity models in spatial prioritizations

IntroductionThe maintenance of habitat connections between fragmented habitat patches is vital for the conservation of wildlife populations and ecosystem functioning. The awareness of connectivity issues for species conservation has resulted in a growth of connectivity modeling and the application of these results in conservation planning. Such connectivity modeling efforts can include several decisions or data limitations, which could influence the connectivity results and ultimately a systematic conservation plan (SCP). However, there has been little investigation of how these different decisions on species, scale, and extent influence the ultimate conservation planning outcomes.MethodsWe modeled the connectivity of northern bobwhite (Colinus virginianus), North American river otter (Lontra canadensis), and black bear (Ursus americanus), three species with varying ecological requirements, through the Congaree Biosphere Region, South Carolina, USA. We modeled habitat suitability for each species using boosted regression trees and converted these results into resistance layers for the connectivity analyses. We compared models for each species at multistate regional and local extents using directional and omnidirectional circuit theory approaches. We then used the results from each modeling combination as conservation goals for three different SCPs to determine how connectivity modeling decisions may influence geographic conservation decisions.ResultsThere was substantial positive spatial correlation between the three connectivity models of each species, and there appeared to be general agreement among mammals as to most important primary corridors. Across all species, the greatest agreement was between the omnidirectional and local directional models as compared with the regional directional plan, which highlighted a unique corridor. The omnidirectional conservation plan required the least amount of planning units to achieve its conservation goals, followed by the local and then regional directional plans that required over 200 km2more land area to be conserved.DiscussionOur results indicate that overall variations in connectivity modeling decisions may have only a moderate impact on the identification of important movement corridors for conservation at the local scale. Practitioners should base modeling decisions on the ecology of the study region, conservation question, and available computing resource.

Effect of fencing on regional ecological networks in the northern Tibetan Plateau.

Fencing is an essential measure for the rehabilitation and conservation of grasslands on the Qinghai-Tibet Plateau. However, its construction could change the distribution and migration of wildlife, thus affecting the integrity of the ecological networks for local wild animal movement. It is of great significance to quantify the potential impact of fencing on ecological network connectivity associated with land-use changes at regional scale. In this study, taking the northern Tibetan Plateau as the study area, we explored the ecological network change using circuit theory approach under different scenarios at county scale. Among them, this study set up four different scenarios according to the economic growth rate, population growth rate and the sustainable development of society and environment. The results showed that: 1) with increased grazing intensity and enhanced human activities from 1990 to 2015, the grasslands of the northern Tibetan Plateau were greatly degraded, most of which was converted into the barren land, and the conversion proportion was as high as 90.84%, which lead to a decreasing trend of the current density of ecological network in most counties and deterioration of ecological connectivity; 2) fencing construction has reduced regional current density, while fencing intensity is positively correlated with current density loss at county scale. Among them, the counties with serious current density loss were distributed in the northwest and southeast regions. The maximum loss ratio is 39.23%; 3) under four different future land use scenarios, coordinated economic, social and environmental development will have a positive effect on the ecological network. The results of the study have important ecological significance for developing reasonable conservation measures for grassland restoration, protecting wildlife, and maintaining regional ecological balance.

Habitat suitability and connectivity modeling predict genetic population structure and priority control areas for invasive nutria (Myocastor coypus) in a temperate river basin.

The nutria (Myocastor coypus), also known as the coypu, is a semi-aquatic, invasive rodent native to South America that causes damage to natural riverine and wetland habitats in many parts of the world, including South Korea. Understanding habitat use, connectivity, and gene flow of nutria populations is critical for the sound management of local and regional ecosystems. Here, we assessed habitat suitability and connectivity in relation to the genetic structure of nutria populations in the Nakdong River Basin of South Korea. A total of 321 nutria occurrence sites and seven environmental variables were used to perform ensemble habitat suitability modeling using five species distribution models (SDMs), including boosted regression trees, maximum entropy model, random forest, generalized linear model, and multivariate adaptive regression splines. Using graph and circuit theory approaches, we assessed the population gene flow and current flow betweenness centrality (CFBC) of suitable habitats derived from the ensemble SDM. All SDMs performed well with a range of test AUC values from 0.962 to 0.970 (mean = 0.966) with true skill statistic values over 0.8. The minimum temperature of the coldest month, mean temperature of the warmest quarter, precipitation of the driest quarter, and distance from water bodies were important predictors in nutria habitat modeling. Nutria population gene flow was significantly correlated with the least-cost path distance on a cost resistance surface based on ensemble habitat suitability modeling and roads (Mantel's r = 0.60, p < 0.05). Finally, the CFBC positively correlated with the genetic diversity of nutria populations was used to identify priority control areas. Habitat suitability and connectivity modeling not only revealed environmental conditions and areas that support the survival and spread of nutrias, but also improved our understanding of the animals' genetic population structure, thereby indicating priority areas to target for eradication.

Terahertz antenna with controllable and tunable filtering characteristics

− A terahertz (THz) wideband antenna is implemented and numerically studied for achieving the controllable and tunable filtering characteristics. A rectangular-shaped metal-based monopole antenna is designed for obtaining the wideband response. A slot is engraved in the radiator to obtain the filtering characteristics. The slot in radiator is filled with graphene material which acts as the controller and tuner of obtained filtering characteristics. The surface conductivity of graphene strip is tuned and hence the field confinement in the covered area is varied which tunes and controls the obtained filtering characteristics. The antenna provides monopole like radiation pattern with a high value of gain and radiation efficiency which decay in the filtered frequency band with a sharp roll-off rate to attain their minimum value. The gain and efficiency of antenna remain approximately unchanged in the passband even after application of graphene in antenna structure. This signifies the effectiveness of the proposed technique for obtaining the filtering characteristics in antenna response. Moreover, the antenna response is validated through an electrical circuit theory approach.

Construction, Evaluation, and Optimization of a Regional Ecological Security Pattern Based on MSPA–Circuit Theory Approach

Ecological security is crucial for regional sustainable development; however, as modern urbanization highlights ecological security challenges, major challenges have arisen. In this paper, we take the ecological region around Taihu Lake, China, as a typical research site, extract important ecological sources and key nodes using morphological spatial pattern analysis (MSPA) and circuit theory, and propose a regulatory framework for the ecological security pattern (ESP) of the ecological region based on the spatial characteristics of sources, corridors, and nodes. We obtained the following results: (1) The ESP includes 20 ecological sources, 37 ecological corridors, 36 critical ecological protection nodes, and 24 key ecological restoration nodes. (2) Most ecological sources are large and concentrated in western Zhejiang and west of Taihu Lake, which are both important ecological sources and ecological resistance surfaces. (3) The ecological corridors spread east, west, and south from Taihu Lake, with high network connectivity. (4) Shanghai serves as the central node, with the Su-Xi-Chang town cluster and the Qiantang River town cluster serving as the extension axes for the ecological resistance hot-spot area. The center of the elliptical ecological resistance surface (standard deviation) lies in Suzhou City, located on the east shore of Taihu Lake. (5) Ecological nodes were mostly located in ecological corridors or junctions. A "four zones and one belt" pattern is suggested in order to make the land around Taihu Lake more connected and stable ecologically. This study can be used as a guide for building and improving an ecological safety network.

Assessing habitat connectivity in environmental impact assessment: a case-study in the UK context

ABSTRACT Ecological connectivity across landscapes is vital for the maintenance of biodiversity and the processes that enable life on earth. Despite this, environmental planning decisions are usually made at the scale of individual projects, failing to account for landscape-scale impacts. Incorporating habitat connectivity analysis in Environmental Impact Assessments (EIAs) could provide an opportunity to address this gap. We present a novel approach to model habitat connectivity in an EIA undertaken for the Heathrow Third Runway Expansion Project, a proposed development in south-east England. Drawing on field data, remote sensing, and species-specific literature reviews, a circuit theory approach was used to assess functional connectivity across the project landscape for grass snakes Natrix helvetica and soprano pipistrelles Pipistrellus pygmaeus. Results indicated key areas for species movement and potential ‘pinch-points’ vulnerable to development impacts. We discuss lessons learnt, potential applications to inform impact assessment, mitigation design, and biodiversity net gain approaches, and further work required to mainstream connectivity analyses in EIA and decision-making.

Spotting what's important: Priority areas, connectivity, and conservation of the Northern Tiger Cat (Leopardus tigrinus) in Colombia.

Leopardus tigrinus is among the least known carnivore species in the Neotropics, including considerable taxonomic uncertainty. Here we model the distribution, connectivity and overlap with existing conservation areas for the species in Colombia. Using a Species Distribution Modeling approach, we estimated current potential range of the species in Colombia and identified potential habitat blocks remaining in the country. In addition, we designed a connectivity network across the available cores, using a circuit theory approach, to evaluate habitat linkage. Finally, we defined a prioritization scheme for the remaining habitat cores and assessed the level of coverage of protected areas for the country. L. tigrinus is potentially present across the three Andean branches of Colombia, with still considerable continuous habitat cores, mostly located on the eastern and central Andean ranges. Most habitat cores are theoretically connected, but nearly 15% are isolated. Priority areas were located across the eastern and central ranges, but with very significant and promising cores in the northern eastern and western ranges. Current level of protection indicates nearly 30% of the range is "protected", but only about 25% is under national strict protected areas. Evolution of this coverage showed some periods of significant increase but interestingly the number of cores grew at a faster rate than overall proportion protected, likely indicating numerous discontinuous fragments, and not contiguous functional landscapes. This represents the most updated assessment of the distribution and conservation status for the species in Colombia, and indicates the numerous conservation opportunities, especially in most populated areas of the country. We found unique business environmental passive's opportunities, including compensation and development potential, which are becoming more available in the country.

Further Qualitative Results for Second-Order Dynamical Systems Based on Circuit Theory Approach

Further Qualitative Results for Second-Order Dynamical Systems Based on Circuit Theory Approach

Circuit theory approach to stability and passivity analysis of nonlinear dynamical systems

AbstractIn this paper, we address the problem of global asymptotic stability and strong passivity analysis of nonlinear time‐varying systems controlled by a second‐order vector differential equation. First, we obtain this equation from a nonlinear time varying network of the circuit theory. Then, we construct the Lyapunov candidate function directly from the physical meaning of the given system. By the way, we review a number of previous results from the point view of Lyapunov's direct method. Our system with its real energy function generalize and improve upon some well‐known studies. The new concept facilitates the formulation of the energy (Lyapunov) function from the power‐energy relationship of the given system. Then, we also realized that the time derivative of the Lyapunov function for a given dynamical systems is the negative value of the power dissipated in the system. Therefore, with the proposed approach, one can inspect the result of the time derivative of the energy function for a given physical system. Finally, two examples (one with simulations) are used to illustrate the superiority and validity of the obtained results.

Modeling an aspirational connected network of protected areas across North America.

Connecting protected areas remains an important global conservation strategy in the face of ongoing and future threats to biodiversity. Amid our growing understanding of how species’ distributions will respond to climate change, conservation scientists need to plan for connectivity conservation across entire continents. We modeled multiscale connectivity priorities based on the least human‐modified lands between large protected areas of North America using least‐cost and circuit theory approaches. We first identified priority corridors between large protected areas, then characterized the network’s structure to unveil priority linkages most important for maintaining network‐ and regional‐level connectivity. Agreement between least‐cost corridors and current flow varied throughout North America, reflecting permeable landscape conditions and “pinch points” where potential ecological flows may concentrate between protected areas. Priority network‐level linkages derived from each approach were similar throughout the continental network (e.g., Rocky Mountains and Canadian boreal), but critical linkages that bridged regional protected‐area networks varied. We emphasize the importance of planning for connectivity at continental scales and demonstrate the utility of multiple methods when mapping connectivity priorities across large spatial extents with wide gradients in landscape conditions.

Landscape connectivity for yellow fever: a proxy approach to detect displacement and circulation through environmental corridors and interfaces

BackgroundYellow fever is an arboviral haemorrhagic disease transmitted by mosquitoes in the tropical regions of Africa and South America. WHO estimates that there are 200 000 severe cases and 30 000 deaths worldwide annually. In Brazil, the wild cycle of yellow fever (also termed urban cycle) occurs through transmission between non-human primates with infected mosquitoes of the Haemagogus and Sabethes genus as intermediaries. Serological analysis of deceased primates is the main monitoring method; however, in many cases, these primates die in remote zones, making the geographical monitoring of yellow fever occurrences difficult. Even so, zoonotic surveillance authorities have observed geographical patterns in yellow fever circulation, especially associated with the ecological connectivity between forest fragments with certain sizes and characteristics. However, several potential displacement corridors connecting geographical points with positive cases remain unknown. Unexpectedly, other routes apparently favourable to primate circulation appear to act as a barrier to yellow fever against displacement. The determination of landscape and ecological characteristics acting on this primate (and viral) circulation is essential for prediction and mapping of displacement corridors and susceptible zones, favouring decision making in planning preventive and proactive actions to combat yellow fever. MethodsWith use of field data for yellow fever-positive primate distribution, we applied landscape connectivity mapping, combining circuit theory and random walk approaches to determine the most environmentally suitable routes or corridors for the displacement of infected primates among positive cases. Based on the extensive experience of zoonotic surveillance authorities in the field, we established a set of relevant variables (eg, forest cover, path sizes, topography, and climate) to generate the resistance surface (ie, a variable that gives ascending values denoting the level of difficulty of an organism to move across the landscape) for São Paulo state, Brazil. FindingsThe preliminary results show a series of potential displacement routes and geographical barriers, providing unprecedented information on environmental affinities and limits for wild yellow fever displacement. These detected routes and points of high susceptibility for yellow fever can be used for field monitoring geographical prioritisation. InterpretationBased on our final results, authorities will be able to define priority sites for primate serological sampling, and determine unsampled and susceptible remote locations where they need to survey for positive or negative cases, filling geographical gaps, and improving the understanding of the wild cycle of yellow fever in Brazil. FundingFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP; 2019/12988-7 and 2018/14389-0).

Exploring the spatio-temporal impacts of farmland reforestation on ecological connectivity using circuit theory: A case study in the agro-pastoral ecotone of North China

Farmland reforestation can contribute substantially to ecological restoration. Previous studies have extensively examined the ecological effects of farmland reforestation, but few of them have investigated the spatiotemporal responses of broad-scale landscape connectivity to reforestation. By using a typical agro-pastoral ecotone in northern China as a case study, we addressed this issue based on an innovative integration of circuit theory approach and counterfactual analysis. The forest connectivity through multiple dispersal pathways was measured using the circuit theory approach, and its spatiotemporal changes after reforestation were evaluated by counterfactual analysis. The results showed that from 2000–2015, the reforested farmland occupied 2095 km2, and 12.5% was on steeply sloped land. Farmland reforestation caused a greater increase in ecological connectivity by adding new ecological corridors and stepping stones in scattered forest areas rather than in areas with dense forest distributions. The newly added corridors and stepping stones were fragmented, short and narrow and thus deserve powerful protection. Future reforestation to improve landscape connectivity should highlight pinch point protection and obstacle removal as well as the tradeoff between farmland loss and farmer survival. Our findings are expected to inform the optimization of the Grain for Green policy from the perspective of broad-scale biodiversity conservation.

Non-uniform lines – review of the theory and measured / simulation examples

This paper reviews existing theories dealing with non-uniform lines both in time domain and in frequency domain. Some papers discussed a non-homogeneous line composed of cascaded homogeneous lines. The theory in the papers neglected lead wires between the cascaded lines. This is mathematically permissible, but physically impossible and thus the theory result in an in-accurate or erroneous solution of the non-homogeneous line. The lead wires are non-uniform because the geometrical configuration at the sending end of the lead wires, i.e. the first homogeneous line, differs from that at the receiving end, i.e. the next homogeneous line. Measured results in time and frequency domains and FDTD computed results are demonstrated for the non-uniform line characteristics. Finally, approximate calculations by a circuit-theory based approach including EMTP are compared with the measured and FDTD computed results, and the limit of the circuit-theory approach is explained.

Multi-layered Graphene Silica-Based Tunable Absorber for Infrared Wavelength Based on Circuit Theory Approach

Graphene can be utilized as a tunable material for a wide range of infrared wavelength regions due to its tunable conductivity property. In this paper, we use Y-shaped silver material resonator placed over the top of multiple graphene silica-layered structures to realize the perfect absorption over the infrared wavelength region. We propose four different designs by placing the graphene sheet over silica. The absorption and reflectance performance of the structures have been explored for 1500- to 1600-nm wavelength range. The proposed design also explores the absorption tunability of the structure for the different values of graphene chemical potential. We have reported the negative impedance for the perfect absorption for proposed metamaterial absorber structures. All the metamaterial absorbers have reported 99% of its absorption peaks in the infrared wavelength region. These designs can be used as a tunable absorber for narrowband and wideband applications. The proposed designs will become the basic building block of large photonics design which will be applicable for polariser, sensor, and solar applications.