scholarly journals Effects of cost surface uncertainty on current density estimates from circuit theory

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9617
Author(s):  
Jeff Bowman ◽  
Elizabeth Adey ◽  
Siow Y.J Angoh ◽  
Jennifer E. Baici ◽  
Michael G.C Brown ◽  
...  
Keyword(s):  
Land Use ◽  
Current Density ◽  
Spatial Configuration ◽  
Landscape Connectivity ◽  
Electrical Current ◽  
Circuit Theory ◽  
Relative Cost ◽  
Density Estimates ◽  
Landscape Elements ◽  
Cost Surface

Background Conservation practitioners are often interested in developing land use plans that increase landscape connectivity, which is defined as the degree to which the landscape facilitates or impedes movement among resource patches. Landscape connectivity is often estimated with a cost surface that indicates the varying costs experienced by an organism in moving across a landscape. True, or absolute costs are rarely known however, and therefore assigning costs to different landscape elements is often a challenge in creating cost surface maps. As such, we consider it important to understand the sensitivity of connectivity estimates to uncertainty in cost estimates. Methods We used simulated landscapes to test the sensitivity of current density estimates from circuit theory to varying relative cost values, fragmentation, and number of cost classes (i.e., thematic resolution). Current density is proportional to the probability of use during a random walk. Using Circuitscape software, we simulated electrical current between pairs of nodes to create current density maps. We then measured the correlation of the current density values across scenarios. Results In general, we found that cost values were highly correlated across scenarios with different cost weights (mean correlation ranged from 0.87 to 0.92). Changing the spatial configuration of landscape elements by varying the degree of fragmentation reduced correlation in current density across maps. We also found that correlations were more variable when the range of cost values in a map was high. Discussion The low sensitivity of current density estimates to relative cost weights suggests that the measure may be reliable for land use applications even when there is uncertainty about absolute cost values, provided that the user has the costs correctly ranked. This finding should facilitate the use of cost surfaces by conservation practitioners interested in estimating connectivity and planning linkages and corridors.

scholarly journals Areas Important for Ecological Connectivity Throughout Canada

2021 ◽  
Author(s):  
Richard Pither ◽  
Paul O'Brien ◽  
Angela Brennan ◽  
Kristen Hirsh-Pearson ◽  
Jeff Bowman
Keyword(s):  
Current Density ◽  
High Current Density ◽  
Circuit Theory ◽  
High Current ◽  
Output Current ◽  
Ecological Connectivity ◽  
Land Cover Data ◽  
Cost Surface ◽  
Spatial Grain ◽  
Density Map

Governments around the world have acknowledged the importance of conserving ecological connectivity to help reverse the decline of biodiversity. In this study we employed recent methodological developments in circuit theory to conduct the first pan-Canadian analysis of multi-species connectivity for all terrestrial regions of the country, at a spatial grain sufficient to support local land-management decisions. We developed a movement cost surface with a limited number of thematic categories using the most recently updated land cover data available for the country. We divided the country into 17 tiles and used a wall-to-wall, omnidirectional mode of Circuitscape on each tile in order to assess ecological connectivity throughout entire landscapes as opposed to strictly among protected areas. The resulting raw current density map of Canada revealed heterogenous patterns of current density across the country, strongly influenced by geography, natural barriers, and human development. We included a validation analysis of the output current density map with independent wildlife data from across the country and found that mammal and herpetofauna locations were predicted by areas of high current density. We believe our current density map can be used to identify areas important for connectivity throughout Canada and thereby contribute to efforts to conserve biodiversity.

scholarly journals Land Use Dynamics and Optimization from 2000 to 2020 in East Guangdong Province, China

2021 ◽  
Vol 13 (6) ◽  
pp. 3473
Author(s):  
Yong Lai ◽  
Guangqing Huang ◽  
Shengzhong Chen ◽  
Shaotao Lin ◽  
Wenjun Lin ◽  
...  
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Landscape Connectivity ◽  
Land Use Changes ◽  
Research Result ◽  
Global Environmental Change ◽  
Ecological Processes ◽  
Buffer Zones ◽  
Conflict Zones ◽  
Land Use Dynamics

Anthropogenic land-use change is one of the main drivers of global environmental change. China has been on a fast track of land-use change since the Reform and Opening-up policy in 1978. In view of the situation, this study aims to optimize land use and provide a way to effectively coordinate the development and ecological protection in China. We took East Guangdong (EGD), an underdeveloped but populous region, as a case study. We used land-use changes indexes to demonstrate the land-use dynamics in EGD from 2000 to 2020, then identified the hot spots for fast-growing areas of built-up land and simulated land use in 2030 using the future land-use simulation (FLUS) model. The results indicated that the cropland and the built-up land changed in a large proportion during the study period. Then we established the ecological security pattern (ESP) according to the minimal cumulative resistance model (MCRM) based on the natural and socioeconomic factors. Corridors, buffer zones, and the key nodes were extracted by the MCRM to maintain landscape connectivity and key ecological processes of the study area. Moreover, the study showed the way to identify the conflict zones between future built-up land expansion with the corridors and buffer zones, which will be critical areas of consideration for future land-use management. Finally, some relevant policy recommendations are proposed based on the research result.

scholarly journals Electrochemical removal of pyrite scale using green formulations

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Musa Ahmed ◽  
Ibnelwaleed A. Hussein ◽  
Abdulmujeeb T. Onawole ◽  
Mohammed A. Saad ◽  
Mazen Khaled
Keyword(s):  
Hydrogen Sulfide ◽  
Current Density ◽  
Iron Sulfide ◽  
Chelating Agent ◽  
Electrical Current ◽  
Electrochemical Process ◽  
Chemical Dissolution ◽  
Hydrocarbon Production ◽  
Rotational Rate ◽  
Diethylenetriamine Pentaacetic Acid

AbstractPyrite scale formation is a critical problem in the hydrocarbon production industry; it affects the flow of hydrocarbon within the reservoir and the surface facilities. Treatments with inorganic acids, such as HCl, results in generation toxic hydrogen sulfide, high corrosion rates, and low dissolving power. In this work, the dissolution of pyrite scale is enhanced by the introduction of electrical current to aid the chemical dissolution. The electrolytes used in this study are chemical formulations mainly composed of diethylenetriamine-pentaacetic acid–potassium (DTPAK5) with potassium carbonate; diethylenetriamine pentaacetic acid sodium-based (DTPANa5), and l-glutamic acid-N, N-diacetic acid (GLDA). DTPA and GLDA have shown some ability to dissolve iron sulfide without generating hydrogen sulfide. The effect of these chemical formulations, disc rotational rate and current density on the electro-assisted dissolution of pyrite are investigated using Galvanostatic experiments at room temperature. The total iron dissolved of pyrite using the electrochemical process is more than 400 times higher than the chemical dissolution using the same chelating agent-based formulation and under the same conditions. The dissolution rate increased by 12-folds with the increase of current density from 5 to 50 mA/cm2. Acid and neutral formulations had better dissolution capacities than basic ones. In addition, doubling the rotational rate did not yield a significant increase in electro-assisted pyrite scale dissolution. XPS analysis confirmed the electrochemical dissolution is mainly due to oxidation of Fe2+ on pyrite surface lattice to Fe3+. The results obtained in this study suggest that electro-assisted dissolution is a promising technique for scale removal.

scholarly journals Effect of Electrical Injection of Corrosion Inhibitor on the Corrosion of Steel Rebar in Chloride-Contaminated Repair Mortar

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
The Huyen Nguyen ◽  
Tuan Anh Nguyen ◽  
Thien Vuong Nguyen ◽  
Van Khu Le ◽  
Thi Mai Thanh Dinh ◽  
...  
Keyword(s):  
Current Density ◽  
Cement Mortar ◽  
Tetrabutylammonium Bromide ◽  
Electrical Current ◽  
Corrosion Current ◽  
Sodium Borate ◽  
Apparent Diffusion Coefficients ◽  
Steel Rebar ◽  
Repair Mortar ◽  
Vis Spectroscopy

The electrical rehabilitation treatments of repair mortar were performed with tetrabutylammonium bromide salt (TBAB) at an electrical current density of 5 A/m2, using two electrolytes (0.1 M NaOH and 0.1 M Na3BO3solutions), and for two time periods (1 and 4 weeks), respectively. The average organic cation-based inhibitor’s concentration in cement mortars before and after this treatment was quantified using the UV-Vis spectroscopy. The experimental results reveal that the EICI treatment with 0.1 M Na3BO3was more effective in injecting the inhibitor and in improving the chloride penetration resistance and compressive strength of the mortar, relative to using 0.1 M NaOH as electrolyte. In this case, after the 4-week EICI treatment, [TBA+] contents were 2.3 % and 2.4% by mass of cement mortar for uncontaminated and salt-contaminated mortars, respectively. After the 4-week EICI treatment, the apparent diffusion coefficients of chloride anion in cement mortar were decreased by 40% from 1.52 × 10−10 m2/s. The EICI treatment was able to halt the chloride-induced corrosion of the steel rebar by promoting its passivation. The 2-week EICI treatment using sodium hydroxide and sodium borate solutions decreased the corrosion current density of the rebar by 77.8% and 78.5%, respectively, approximately two months after the treatment.

The sensitivity of least-cost habitat graphs to relative cost surface values

2009 ◽  
Vol 25 (4) ◽  
pp. 519-532 ◽  
Author(s):  
Bronwyn Rayfield ◽  
Marie-Josée Fortin ◽  
Andrew Fall
Keyword(s):  
Relative Cost ◽  
Cost Surface
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