28 results on '"POTENTIAL distribution"'
Search Results
2. Littleseed canarygrass (<italic>Phalaris minor</italic> Retz.) a major weed of rice-wheat system in India is predicted to experience range contraction under future climate.
- Author
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Gharde, Yogita, Dubey, R. P., Singh, P. K., and Mishra, J. S.
- Abstract
Abstract Modelling was carried out using maximum entropy model (MaxEnt) to explore and predict the invasion potential of littleseed canarygrass (
Phalaris minor Retz.) in India under current as well as future climatic conditions under Representative Concentration Pathways (RCPs) 4.5 and 8.5 for the years 2050 and 2070. Mutually least correlated 8 bioclimatic variables along with soil and elevation data were used for the modelling over 223 occurrence locations of the species. Jackknife test revealed the significance of temperature derived variablesviz . temperature seasonality, annual mean temperature and minimum temperature of the coldest month in governing the potential distribution ofP. minor . Currently, 21% of India’s area is either highly (9%) or moderately (12%) suitable as habitat forP. minor . Our model predicts approximately 90% contraction in the area considered to be highly or moderately suitable climatically between 2050 and 2070 under both moderate and high emissions scenarios. Thus, under future climate, a significant niche shift by the species and decreased suitability was observed compared to the current distribution. The present study is first of its kind in exploring the invasion potential of alien invasive weedP. minor under climate change scenarios which is a current threat to rice-wheat system in Indo-Gangetic plains of India. [ABSTRACT FROM AUTHOR]- Published
- 2023
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3. Synthesis of hydroxyapatite containing iron ions by soft solution method and evaluation of photo-Fenton reaction.
- Author
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Saeki, Shogo and Nonami, Toru
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HYDROXYAPATITE synthesis , *LATTICE constants , *METHYLENE blue , *IRON ions , *EVALUATION methodology , *ADSORPTION capacity - Abstract
Hydroxyapatite (HAp) is widely studied owing to its high adsorption capacity for various substances. In this study, HAp containing iron ions (FeAp) was synthesised by a simulated body fluid method, and the solid-solution state of iron in FeAp crystals was investigated to evaluate the photo-Fenton reaction. The crystalline phase and lattice parameters of the sample were determined through X-ray diffraction analysis. The lattice parameters revealed lattice contraction along the a-axis direction for FeAp, indicating the incorporation of Fe ions. The results of methylene blue decolourisation experiments and potential measurements with a scanning probe microscope before and after the addition of H2O2 suggested that FeAp undergoes a photo-Fenton reaction. Thus, it was confirmed that iron in the crystals contributed to the photo-Fenton reaction. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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4. Distribution modelling of the rare stink bug Ceratozygum horridum (Germar, 1839): isolated in small spots across the Neotropics or a continuous population?
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Perger, Robert, do Amaral, Karina Bohrer, and Bianchi, Filipe Michels
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STINKBUGS , *TROPICAL dry forests , *ENDANGERED species , *SPECIES distribution , *HEMIPTERA , *ALGORITHMS - Abstract
Cyrtocorinae species are morphologically remarkable stink bugs (Heteroptera: Pentatomidae) from the Neotropics. Ceratozygum horridum (Germar, 1839) is a little-known species with scarce occurrence data but presenting a broad and discontinuous distribution in Amazon and Atlantic Forest, lacking records in the dry diagonal. Field trips in Bolivia registered new records of C. horridum in an ecotone between the Southwest Amazon forest, the Chiquitano Dry Forest and the Dry Chaco forest. We used the maximum entropy algorithm aiming to model the occurrence probability of C. horridum on the Amazon Forest and transferred this model to the dry diagonal and the Atlantic Forest looking for continuous areas of probable occurrence for this species. We used ten records for a constrained portion of the Amazon forests and four environmental layers to train models with different numbers of background points. The average model performances returned AUC values higher than 0.7 and maximum sensitivity was reached. The models could not predict species occurrence with reliability when transferred to the whole Amazon area, dry diagonal, and the Atlantic Forests. Our findings suggest a low probability of occurrence of C. horridum in the dry diagonal, supporting the hypothesis that the Amazon and Atlantic Forests populations are isolated by the dry diagonal. The populations of C. horridum seem to be isolated in small spots with dissimilar ecological features across the complex ecoregions of the Neotropics. Building species distribution models for species with poorly known distribution is challenging and may raise more questions than light answers. Even the small pieces of evidence are pertinent to the knowledge of rare species like C. horridum. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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5. Spectroscopic investigation, molecular orbital studies, frequency and solvent dependent NLO properties of (2E)-1-(4-bromophenyl)-3-phenylprop-2-en-1-one.
- Author
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Balachandran, V., Anitha, K., Narayana, B., Karunanidhi, M., and Revathi, B.
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MOLECULAR orbitals , *IONIZATION energy , *CHEMICAL potential , *POTENTIAL energy , *ELECTRON affinity , *FRONTIER orbitals ,POTENTIAL distribution - Abstract
The structure and the vibrational frequencies of the fundamental modes of the optimized geometry of (2E)-1-(4-bromophenyl)-3-phenylprop-2-en-1-one (BP3PP) have been determined. A detailed vibrational spectral analysis was carried out and the assignments of the observed bands have been proposed on the basis of potential energy distribution (PED). The UV-Vis spectral analysis has been performed by the TD – DFT method at the CAM-B3LYP/6–31 + G (d) level in gas phase and different solvent phase. Other molecular properties such as ionization energy, electron affinity, chemical potential, global hardness and electrophilicity were also calculated. The static and dynamic (frequency) average polarizability (α), first- and second- order hyperpolarizabilities (β and γ) have been investigated by using the CAM-B3LYP method. The solvent effects on the polarizability (α), first- and second- order hyperpolarizabilities (β and γ) have also been evaluated by IEFPCM model. The results display significant second- and third-order molecular nonlinearity of the title compound. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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6. Landscape and niche specialisation of two brush-tailed mice species Calomyscus elburzensis and C. hotsoni in Iran: a case of the role of ecological niche modelling in finding area(s) of contact.
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Hamidi, Kordiyeh, Matin, Maryam M., Kilpatrick, C. William, and Eskandarzadeh, Naeimeh
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ECOLOGICAL models , *ECOLOGICAL niche , *HABITAT selection , *SPECIES distribution , *DATA distribution , *MICE ,POTENTIAL distribution - Abstract
Brush-tailed mice (family Calomyscidae) are small rodents found on the Iranian plateau and surrounding areas. To date, little discussion of the ecological aspects, habitat suitability and niche differentiation has been provided for members of this family. Herein, to model the potential distributions and describe habitat preferences of Calomyscus elburzensis and C. hotsoni, the maximum entropy modelling (MaxEnt) approach was used based on data collected through field expeditions, review of the literature and various databases. Species distribution modelling showed that minimal temperature of the coldest month and precipitation of the coldest quarter were the most important factors in predicting the distribution of C. elburzensis. However, occurrence of C. hotsoni was affected greatly by isothermality and annual precipitation. The mountainous regions in northeastern Iran, the central portions of the Elburz Mts, and the eastern hillsides of the Zagros Mts were identified as the most suitable habitats for C. elburzensis, whereas the western parts of South Khorasan province, the forest steppes in the southeast of Iran, and the southwestern extension of the Jebal Barez Mts in central Iran were highly suitable for C. hotsoni. Measurement of ecological niche overlaps showed low similarity between the niches of these two species. Nevertheless, the modelling identified areas of suitable habitat in the north centre parts of both South Khorasan and Kerman provinces where both or either of these species could occur. Moreover, C. elburzensis inhabited cold mountains, Mediterranean, and cold semi-desert climatic conditions, whereas C. hotsoni was generally showed high level of habitat suitability to hot dry desert and hot semi-desert climatic conditions. C. elburzensis mainly inhabits forest steppe and semi-desert biotopes, whereas C. hotsoni occupies desert lowlands in addition to forest steppe and semi-desert biotopes. Further studies are needed to resolve the distribution of each species and to follow their interactions in potential contact zones. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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7. Compounded inverse Weibull distributions: Properties, inference and applications.
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Chakrabarty, Jimut Bahan and Chowdhury, Shovan
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WEIBULL distribution , *GEOMETRIC distribution , *POISSON distribution , *STATISTICAL reliability , *EXPECTATION-maximization algorithms ,POTENTIAL distribution - Abstract
In this paper two probability distributions are analyzed which are formed by compounding inverse Weibull with zero-truncated Poisson and geometric distributions. The distributions can be used to model lifetime of series system where the lifetimes follow inverse Weibull distribution and the subgroup size being random follows either geometric or zero-truncated Poisson distribution. Some of the important statistical and reliability properties of each of the distributions are derived. The distributions are found to exhibit both monotone and non-monotone failure rates. The parameters of the distributions are estimated using the expectation-maximization algorithm and the method of minimum distance estimation. The potentials of the distributions are explored through three real life data sets and are compared with similar compounded distributions, viz. Weibull-geometric, Weibull-Poisson, exponential-geometric and exponential-Poisson distributions. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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8. Predicting the distribution of harmful species and their natural enemies in agricultural, livestock and forestry systems: an overview.
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Lantschner, M. Victoria, de la Vega, Gerardo, and Corley, Juan C.
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SPECIES distribution , *INSECT pests , *LIVESTOCK , *INTRODUCED species , *BIOLOGICAL pest control ,POTENTIAL distribution - Abstract
Predicting the potential distribution of harmful species to agriculture, livestock and forestry is decisive to prevent their impacts, especially when these are expanding their range due to global change. Recent advances in species distribution modelling (SDM) have made these tools widely used for biosecurity studies. We reviewed the available literature of SDM for pest, weeds, pathogen species and biological-control agents, with the aims of synthesizing and quantifying the available information, and identifying gaps in the knowledge and future perspectives. SDMs for 420 species were collected from 220 publications. Insect pests were the most frequently studied organisms. CLIMEX and MaxEnt were the most commonly used modelling tools, while pure mechanistic approaches were rarely applied. Most studies covered broad scales, and focused on predicting the distribution of invasive species and/or the effects of climate change. The challenge remains for models to include disturbance, resource availability, and biotic factors, as well as to better quantify uncertainty. This future directions will be fundamental to improve the predictive power of SDMs for productive systems in the context of a rapidly changing World. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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9. Distribution and diversity of leaf-cutting ants in Northeastern Argentina: species most associated with forest plantations.
- Author
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Sánchez-Restrepo, Andrés F., Jiménez, Nadia L., Confalonieri, Viviana A., and Calcaterra, Luis A.
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LEAF-cutting ants , *TREE farms , *CLEARCUTTING , *INSECT pests , *ECOLOGICAL models , *ECOLOGICAL niche ,POTENTIAL distribution - Abstract
Leaf-cutting ants (LCA) are considered one of the main herbivores and one of the most destructive pest insects of the Neotropics. Northeastern Argentina harbors the greatest species richness of these ants and in turn comprises the highest surface with forest plantations. Our aim was to establish which species of leaf-cutting ants are most commonly associated with forest plantations by analyzing their geographic distribution using published and unpublished species occurrence data. Also, estimate their potential areas of distribution along a latitudinal gradient that entirely encompasses northeastern Argentina using Ecological Niche Modeling. Only seven of the 20 species recorded were strongly associated with productive systems along the gradient, but only 2–3 species in each region could be considered high-risk species for forest plantations. High-risk species composition shows a turnover between regions. Our models show the potential distribution areas where LCA could become more abundant and dominant, and possibly causing a detrimental effect on the forest plantations in the studied region. We find that ecological niche models are useful tools to assess the environmental suitability of important LCA. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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10. Drosophila suzukii (Diptera: Drosophilidae) distribution modelling improves our understanding of pest range limits.
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de la Vega, Gerardo J. and Corley, Juan C.
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DROSOPHILA suzukii , *DROSOPHILIDAE , *DIPTERA , *CURRENT distribution , *PEST control ,POTENTIAL distribution - Abstract
Spatial distributions models (SDM) are often used in invasive pest management to understand current and potential distribution. Using data on the well-studied spotted wing drosophila as a model, we compared distribution patterns of the range-limit with commonly applied correlative and mechanistic models. Correlative models risk underestimation whereas simple mechanistic models provide overestimated range predictions, although using both approaches for the spotted wing drosophila improved range-limit predictions. Model choice when dealing with pests is central to the accurate identification of invasive species limit range and consequently for the deployment of monitoring and early detection programs. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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11. Modeling of Drain Induced Barrier Lowering Effect for Bi-Material Buffer Gate 4H-SiC Metal Semiconductor Field Effect Transistor.
- Author
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Zhang, Xianjun, Wang, Mingjia, Qin, Qingliang, and You, Na
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METAL semiconductor field-effect transistors , *THRESHOLD voltage ,POTENTIAL distribution - Abstract
A novel bi-material buffer gate 4H-SiC metal semiconductor field effect transistor (BMGFET) is proposed for the purpose of restraining the drain-induced barrier lowering (DIBL) effect. The analytical model of the DIBL effect for the BMGFET is built and its occurrence degree is evaluated by analyzing the dependence of the threshold voltage shift and the sub-threshold slope factor on the drain bias and the structure parameters. The results reveal that the DIBL effect is significantly suppressed because there appears a valley in the graph of the potential distribution function of the BMG structure. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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12. The Economic Implications of Robinia pseudoacacia L. (black locust) on Agricultural Production in South Africa.
- Author
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Humphrey, Luke, Fraser, Gavin, and Martin, Grant
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BLACK locust , *AGRICULTURAL productivity , *ECONOMIC impact , *GROSS margins ,POTENTIAL distribution - Abstract
Robinia pseudoacacia L. (black locust) is an invasive deciduous, broad-leaved tree that has the potential to be widely distributed across South Africa. It has invaded all nine South African provinces. The potential economic impact of R. pseudoacacia on agricultural production stems from the tree's ability to reduce the carrying capacity for livestock. This study estimated the potential economic implications of R. pseudoacacia on agricultural production in South Africa, specifically the livestock sector. R. pseudoacacia's potential distribution was calculated by using a maximum-entropy predictive habitat model, MaxEnt. The distribution of livestock, based on grazing capacity (ha/large stock unit) in South Africa, was then determined. The potential direct economic impacts were estimated by assessing the impact of the potential distribution of R. pseudoacacia on the carrying capacity for livestock. The results showed that an infestation of R. pseudoacacia has the potential to reduce the total gross margin in the livestock sector by between approximately R135 million and R674 million, dependent on the level of invasion. The potential levels of foregone income and business activity found in this study reaffirm the need to devote resources to develop a viable, economical and effective control. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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13. Centaurea subsect. Phalolepis in Southern Italy: ongoing speciation or species overestimation? Genetic evidence based on SSRs analyses.
- Author
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Garcia-Jacas, Núria, López-Pujol, Jordi, López-Vinyallonga, Sara, Janaćković, Pedja, and Susanna, Alfonso
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CENTAUREA , *MICROSATELLITE repeats , *LAST Glacial Maximum , *GENETIC speciation , *ECOLOGICAL niche , *SPECIES ,POTENTIAL distribution - Abstract
In this paper, we investigated a set of narrow endemics of Centaurea subsect. Phalolepis from the mountains of South Italy (mainly Calabria and Salento), segregated from the widespread species Centaurea deusta, using microsatellite (SSR) markers. The goal was to analyse the genetic makeup (levels and structure) of C. deusta and the segregated species and verify whether genetic clusters were in agreement with current classification of the species. With C. deusta, we also carried out an ecological niche modelling (ENM) analysis to check its potential distribution under present climatic conditions and to project it to the Last Glacial Maximum (LGM). As also found in former studies with subsect. Phalolepis in Greece and Turkey using the same set of SSRs, genetic diversity for the segregated Italian species was higher than expected for narrow endemics with small populations. Genetic clusters, however, were not correlated with the described species and did not support the segregation of the purported narrow endemics from a widely defined C. deusta. The results of the ENM indicate that the Adriatic Sea was a migration corridor for C. deusta at the LGM. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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14. Integrative taxonomy reveals the exceptional species diversity of Eudonia (Lepidoptera: Crambidae) in Tibet, China.
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Li, Weichun
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SPECIES diversity , *SPATIAL variation , *TAXONOMY , *CRAMBIDAE , *LEPIDOPTERA - Abstract
The genus Eudonia is rarely recorded in Tibet despite having a wide occurrence in the plateau. In the taxonomy of the genus, the morphological characters are insufficient to delimit the closely related congeners due to the subtly interspecific differences and conspicuously intraspecific variability. In this study, the Tibetan species are studied with an integrative approach using molecular data and morphological characters. It is found that the number of Eudonia species in Tibet accounts for about 20% of the total species previously catalogued for the genus in China. Five species are described as new to science: Eudonia galonglaensis Li, sp. nov., E. varians Li, sp. nov., E. triangulata Li, sp. nov., E. angusta Li, sp. nov., and E. bomiensis Li, sp. nov. The potential distribution of Chinese Eudonia is predicted and illustrated using MaxEnt and DIVA-GIS. The results reveal the exceptionally high species diversity of Eudonia in Tibet for the first time, demonstrate that the integrative morphological and molecular approach is highly effective for resolving the difficult-to-distinguish morphologies, and predict the region of China to the south of 35°N and to the east of 95°E as having potentially high Eudonia species diversity. http://www.zoobank.org/urn:lsid:zoobank.org:pub:EA3C5D21-9674-46E4-838D-48D5A098314B [ABSTRACT FROM AUTHOR]
- Published
- 2019
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15. Effect of external load resistance on Rosen transformer surface electrical potential.
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Stekke, Jordan and Pigache, François
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SURFACE potential , *MECHANICAL models , *MODEL validation ,POTENTIAL distribution - Abstract
This work is about the modeling and experimental validation of the electrical potential distribution on Rosen piezoelectric transformer surface. In a first step, we carry out a linear analytical multi-modal model of electrical and mechanical properties of the PT with its resistive load dependency. Then, we discuss this model compared to experimental results carried out on a commercial multi-layer PT. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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16. Three-dimensional generalized thermoelastic diffusion and application for a thermoelastic half-space subjected to rectangular thermal pulse.
- Author
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Youssef, Hamdy M. and Al-Lehaibi, Eman A. N.
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DIFFUSION , *THERMOELASTICITY , *LAPLACE transformation , *CHEMICAL potential ,POTENTIAL distribution - Abstract
In this article, a model of three-dimensional generalized thermo-diffusion in a half-space thermoelastic medium subjected to permeating gas and the rectangular thermal pulse has been constructed. The half-space is considered to be made of an isotropic homogeneous thermoelastic material. The chemical potential is also assumed to be known on the bounding plane. Laplace transform techniques have been applied, and the solution is obtained in the Laplace transform domain using a direct approach. The solution of the problem in the physical domain is obtained numerically using a numerical method based on a Riemann-sum approximation for the inversion of Laplace transform. The temperature increment, stress, strain, diffusion concentration, and chemical potential distributions are represented graphically. The nonzero value of the relaxation time parameter predicts the finite speed of thermal, mechanical, diffusion waves. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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17. The effect of boundary conditions on epicardial potential distributions.
- Author
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Barnes, Josef P. and Johnston, Peter R.
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ISCHEMIA , *BOUNDARY value problems , *FOURIER transforms , *NUMERICAL analysis , *MATHEMATICAL models ,POTENTIAL distribution - Abstract
This study presents a comparison of semi-analytical and numerical solution techniques for solving the passive bidomain equation in simple tissue geometries containing a region of subendocardial ischaemia. When the semi-analytical solution is based on Fourier transforms, recovering the solution from the frequency domain via fast Fourier transforms imposes a periodic boundary condition on the solution of the partial differential equation. On the other hand, the numerical solution uses an insulation boundary condition. When these techniques are applied to calculate the epicardial surface potentials, both yield a three well potential distribution which is identical if fibre rotation within the tissue is ignored. However, when fibre rotation is included, the resulting three-well distribution rotates, but through different angles, depending on the solution method. A quantitative comparison between the semi-analytical and numerical solutiontechniques is presented in terms of the effect fibre rotation has on the rotation of the epicardial potential distribution. It turns out that the Fourier transform approach predicts a larger rotation of the epicardial potential distribution than the numerical solution. The conclusion from this study is that it is not always possible to use analytical or semi-analytical solutions to check the accuracy of numerical solution procedures. For the problem considered here, this checking is only possible when it is assumed that there is no fibre rotation through the tissue. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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18. Potential risk of occurrence of Phytophthora alni in forests of the Czech Republic.
- Author
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Romportl, Dušan, Chumanová, Eva, Havrdová, Ludmila, Pešková, Vítězslava, and Černý, Karel
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PHYTOPHTHORA , *INTRODUCED fungi , *FORESTS & forestry - Abstract
Phytophthoraalniis an invasive organism that causes root and collar rot in alders, which significantly damages the forest and riparian vegetation of alder trees in Central and Western Europe. In the Czech Republic, this pathogen was first confirmed in 2001, and since then it has been gradually spreading from the west to the east. Here, we applied a model of potential distribution that estimates the level and spatial variability of the pathogen occurrence and spread risk for Czech Republic forests to target the early detection and control the further invasion ofP. alniin this region. Our predictions are based on a rigorous statistical analysis of data obtained from field survey as well as available geodatabases. We used two sets of predictor variables describing (i) the forest stands and (ii) neighbourhood of the stands, and generalized linear modelling with forward stepwise selection of predictors. The results of statistical analysis showed the significant effect of the area of the forest stand, forest vegetation zone, presence of watercourse and area of alder stands in the neighbourhood on the probability of occurrence ofP. alniin the study region. The map derived based on the final model shows the potential risk of occurrence and impact ofP. alniin forests of the Czech Republic as classified on a five-point scale ranging from very low risk for alder stands with a low level of likely invasion to very sensitive alder stands with high probability of pathogen occurrence and high levels of damage. This is a unique output not only for the Czech Republic but also throughout Europe. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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19. Quasi-static analysis of scattering from a layered plasmonic sphere in fractional space.
- Author
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Noor, Ahsan, Syed, Aqeel A., and Naqvi, Qaisar A.
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SCATTERING (Physics) , *PLASMONICS , *POLARIZABILITY (Electricity) , *NUMERICAL analysis ,POTENTIAL distribution - Abstract
Quasi-static analysis of scattering from a layered sphere in fractional dimensional space is presented. The layers to be considered include plasmonic and/or non-plasmonic materials. Additionally, the space surrounding and occupied by the sphere is assumed to be fractional. The effects of layers and fractionality of dimensions on polarizability and potential distribution of the sphere are investigated. Numerical results for the same are presented for various combinations of layers and fractionality of the space. [ABSTRACT FROM PUBLISHER]
- Published
- 2015
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20. Study on operating properties of ceramic long rod insulator for transmission line.
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Gao, S., Liu, Y., Zhu, M. X., Tao, F. B., Zhou, Z. C., Bo, B., and Huang, Y. J.
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ELECTRIC insulators & insulation , *ELECTRIC lines , *FINITE element method , *COMPOSITE materials , *MATERIALS science - Abstract
The material prescription, potential distribution, contamination trend and surface insulating properties under contamination and lightning conditions for the ceramic long rod insulator are investigated. The surface contamination trend of the ceramic long rod insulator can be fitted to an exponential function in a low rainfall area. Potential distribution calculation by three-dimensional finite element method shows that over 50% operating voltage concentrates on the single unit of high-voltage polarity for the long rod insulator string, which is more uneven in comparison with the disc ceramic insulator string. Five-hundred kilovolt full-scale artificial pollution test demonstrates that the contamination flashover voltage of the ceramic long rod insulator has a negative exponential relationship with equivalent salt deposit density and a linear relation with string length. A lightning impulse discharge test confirmed that the relation between 50% lightning impulse discharge voltage and dry arcing distance was also linear for a ceramic long rod insulator string. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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21. Analysis of Stress Control on 33-kV Non-ceramic Insulators Using Finite-element Method.
- Author
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Natarajan, Murugan, Basharan, Vigneshwaran, Pillai, Kannayeram Ganapathya, Velayutham, Maheswari Ramasamy, and Silluvairaj, Willjuice Iruthayarajan Maria
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ELECTRIC controllers , *CERAMIC insulators , *FINITE element method , *ELECTRIC fields ,POTENTIAL distribution - Abstract
In this article, analysis of electric field stress and electric potential distributions of a 33-kV composite insulator and factors that affect the electric field are discussed. Accordingly, the article is classified into two parts. In the first part, the designs of three different configurations of non-ceramic (composite) insulator based on their geometry modification in end fittings and water shed are discussed. The electrical performances are analyzed using electric field and electrical potential distribution. In the second part, a reduction of the electric field near the end fittings is done to control the electric field stress intended for long-term performance. For that, the grading material is placed between the core and housing materials by fitting the arcing horn near the end fittings. A 33-kV composite insulator is modeled in two dimensions by the finite-element method to investigate the electric field and electric potential distribution under normal and polluted conditions. The results reveal that an optimum installation of an arcing horn at the high-voltage end in the composite insulator with silicone rubber overlapping the edges of metal end fittings made a significant reduction in electric field stress on 33-kV non-ceramic insulators. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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22. Monitoring and modeling the invasion of the fast spreading alien Senecio inaequidens DC. in an alpine region.
- Author
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Vacchiano, G., Barni, E., Lonati, M., Masante, D., Curtaz, A., Tutino, S., and Siniscalco, C.
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SENECIO , *PLANT invasions , *INTRODUCED plants , *MOUNTAIN plants , *PHYTOGEOGRAPHY , *LAND use - Abstract
We modeled the distribution of the South African alienSenecio inaequidensDC. in the Aosta Valley, Western Italian Alps, using data extracted from the Regional floristic database and from an intensive field survey carried out in years 2009–2010. The aims of the work were (1) to evaluate whether the species is in the introduction, colonization, or establishment stage of invasion, (2) to detect the environmental factors that drive the invasion process, and (3) to highlight the potential range of distribution of the alien species. The modeling framework was a stepwise generalized linear model (GLM), using gridded presence/absence data and environmental predictors such as topography, climate, land use, and anthropogenic and natural disturbances. GLM were fit both with and without an additional independent variable to take into account current dispersal limitations.S. inaequidensdisplayed a very fast spread in the Aosta Valley in the years 1990–2010. The species was positively associated with roads and rivers, southern slopes, and negatively with elevation. However, it was found at an elevation of 1600 m, showing the ability to reach higher elevations than those observed for other invasive alien species, and confirming to be pre-adapted to mountain conditions. The difference between the species distribution models, with and without dispersal constraints, suggested that the availability of seed sources still limits the potential distribution of the species, rather than the environmental variables, and that the realized regional niche differs to a great extent from the equilibrium niche. When limitations to the seed source cease (i.e., in the establishment stage), the species will likely invade large areas that are currently characterized by pastures and grasslands with native species of high agricultural importance. The invasion ofS. inaequidensshould therefore be considered a serious threat, due to its potential to invade mountain regions, and in particular to colonize habitats used for grazing and forage, thus leading to a high risk for cattle and human health. We discuss the relevance of the results both concerning communication with the public and to support local eradication and control activities. The inclusion ofS. inaequidensin the “black list” of the regional law for the conservation of alpine flora (L.R. 45/2009) will help to transfer the information and support invasion control, in particular at medium elevations. [ABSTRACT FROM PUBLISHER]
- Published
- 2013
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23. Influence of positional accuracy, sample size and scale on modelling species distributions: a review.
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Moudrý, Vítězslav and Šímová, Petra
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SPECIES distribution , *BIOGEOGRAPHY , *ANIMAL ecology , *ECOLOGICAL niche , *WILDLIFE conservation - Abstract
Species distribution models (SDMs) are an important tool in biogeography and ecology and are widely used for both fundamental and applied research purposes. SDMs require spatially explicit information about species occurrence and environmental covariates to produce a set of rules that identify and scale the environmental space where the species was observed and that can further be used to predict the suitability of a site for the species. More spatially accurate data are increasingly available, and the number of publications on the influence of spatial inaccuracies on the performance of modelling procedures is growing exponentially. Three main sources of uncertainty are associated with the three elements of a predictive function: the dependent variable, the explanatory variables and the algorithm or function used to relate these two variables. In this study, we review how spatial uncertainties influence model accuracy and we propose some methodological issues in the application of SDMs with regard to the modelling of fundamental and realized niches of species. We distinguish two cases suitable for different types of spatial data accuracy. For modelling the realized distribution of a species, particularly for management and conservation purposes, we suggest using only accurate species occurrence data and large sample sizes. Appropriate data filtering and examination of the spatial autocorrelation in predictors should be a routine procedure to minimize the possible influence of positional uncertainty in species occurrence data. However, if the data are sparse, models of the potential distribution of species can be created using a relatively small sample size, and this can provide a generalized indication of the main regional drivers of the distribution patterns. By this means, field surveys can be targeted to discover unknown populations and species in poorly surveyed regions in order to improve the robustness of the data for later modelling of the realized distributions. Based on this review, we conclude that (1) with data that are currently available, studies performed at a resolution of 1–100 km2 are useful for hypothesizing about the environmental conditions that limit the distribution of a species and (2) incorporating coarse resolution species occurrence data in a model, despite an increase in sample size, lowers model performance. [ABSTRACT FROM PUBLISHER]
- Published
- 2012
- Full Text
- View/download PDF
24. Find Your Niches: A Guide for Managing Intermedia Effects Among Content Distribution Channels.
- Author
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Mann, Florian, Mahnke, Rolf, and Hess, Thomas
- Subjects
- *
CONJOINT analysis , *MOTION picture distribution , *DIGITAL cinematography , *BROADBAND communication systems , *MARKETING channels , *INTERNET ,POTENTIAL distribution - Abstract
Content providers such as movie studios that embrace the Internet as an additional distribution channel are encountering the issue of measuring and managing intermedia effects. In multichannel distribution arrangements, content owners and distributors must know whether channels will cannibalize or complement one another and the circumstances under which such behavior will occur. With this knowledge, content providers can depart from merely describing cross-media effects and move toward managing cross-media. The authors present a five-step guide for measuring and managing cross-media effects on media content in multichannel distribution environments. The analytical framework builds on the ecological theory of the niche, which states that the intensity of intermedia competition depends on the degree of differentiation among channels. This framework is the first attempt to combine niche theory with conjoint analysis to develop a method of data collection and analysis. The use of the five-step guide is demonstrated with preference data from a quantitative survey of 552 potential consumers of digital movies. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
25. COMPUTATIONAL MODEL OF THE MARK-IV ELECTROREFINER: TWO-DIMENSIONAL POTENTIAL AND CURRENT DISTRIBUTIONS.
- Author
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HOOVER, ROBERT O., PHONGIKAROON, SUPATHORN, SIMPSON, MICHAEL F., TAE-SIC YOO, and LI, SHELLY X.
- Subjects
- *
CONDUCTIVITY of electrolytes , *FUSED salts , *ELECTRIC conductivity - Abstract
A computational model of the Mark-IV electrorefiner is currently being developed as a joint project between Idaho National Laboratory, Korea Atomic Energy Research Institute, Seoul National University, and the University of Idaho. As part of this model, the two-dimensional potential and current distributions within the molten salt electrolyte are calculated for U3+, Zr4+ and Pu3+ along with the total distributions, using the partial differential equation solver of the commercial Matlab software. The electrical conductivity of the electrolyte solution is shown to depend primarily on the composition of the electrolyte and to average 205 mho/m with a standard deviation of 2.5 x 10-5% throughout the electrorefining process. These distributions show that the highest potential gradients (thus, the highest current) exist directly between the two anodes and cathode. The total, uranium, and plutonium potential gradients are shown to increase throughout the process, with a slight decrease in that of zirconium. The distributions also show small potential gradients and very little current flow in the region far from the operating electrodes. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
26. Calculation of Voltage Distribution along Porcelain Suspension Insulators Based on Finite Element Method.
- Author
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Ashouri, Mehdi, Mirzaie, Mohammad, and Gholami, Ahmad
- Subjects
- *
NUMERICAL analysis , *ELECTRIC potential , *FINITE element method , *PORCELAIN , *POWER transmission , *ELECTRICAL conductors - Abstract
Porcelain string insulators are widely used in high-voltage transmission lines. Calculation of potential distribution is extensively performed in the design and development of high-voltage insulators. This article applies a three-dimensional electromagnetic analysis program to calculate the potential distribution of 230-kV porcelain suspension insulators under clean and dry conditions. The effects of cross-arm length, number of units, corona ring parameters, and also effects of wind force on the potential distribution along the porcelain suspension insulators are investigated and discussed. The results are useful for analyzing the potential distribution for porcelain suspension insulators. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
27. Translating natural history into geographic space: a macroecological perspective on the North American Slider, Trachemys scripta (Reptilia, Cryptodira, Emydidae).
- Author
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Rödder, Dennis, Kwet, Axel, and Lötters, Stefan
- Subjects
- *
TRACHEMYS scripta , *SEXING of animals , *CLIMATE change , *BIOLOGICAL research , *SPECIES distribution , *MACROECOLOGY - Abstract
Species with temperature-dependent sex determination, such as the Slider, Trachemys scripta, from North America, may be particularly dependent on certain climatic conditions. We hypothesize that climatic conditions that allow successful egg incubation and balanced sex ratios in T. scripta are the major driver for the species' geographic distribution. We tested whether the observed variation in monthly mean temperatures from 377 records throughout the native distribution of T. scripta can be used as a predictor for its geographic range. Our study showed that climatic requirements during egg incubation are apparently the major driver for the species' geographic distribution. Freezing events during winter may limit the species' distribution regionally only. Adaptive strategies such as nest site choice by females, plasticity in nesting phenology or regional variation in embryonic temperature sensitivity exist. However, they may account for only partial compensation of negative effects caused by regional differences in temperature-related parameters or a changing climate. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
28. Numerical Algorithm to Solve the Poisson-Boltzmann Equation in Rectangular Coordinates for High Surface Potentials.
- Author
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Márquez-Riquelme, EstebanF. and García-Rubio, LuisH.
- Subjects
- *
POISSON'S equation , *DIFFERENTIAL equations , *DIFFERENTIAL geometry , *ELECTROLYTES , *COORDINATES , *SOLUTION (Chemistry) , *NUMERICAL analysis - Abstract
The Poisson-Boltzmann equation is set for multiple general electrolytes in rectangular coordinates, and a numerical method is developed to solve it for a wide range of constant surface potentials. An expression to calculate the free energy of repulsion for mixtures of symmetrical and asymmetrical electrolytes is then derived following the method of Bell and Peterson (1972). The electric double-layer potential distribution calculated with the numerical method compares very accurately to approximations from the literature. Unlike most of the approximate solutions and methods proposed previously, the numerical solution developed in this work can handle many types of symmetrical and asymmetrical electrolytes as well as mixtures of them. The results presented explore some features of the behavior of constant potential plates immersed in mixtures of electrolytes in solution. [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
- View/download PDF
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