scholarly journals The impact of different aperture distribution models and critical stress criteria on equivalent permeability in fractured rocks

2016 ◽  
Vol 121 (5) ◽  
pp. 4045-4063 ◽  
Author(s):  
Kevin Bisdom ◽  
Giovanni Bertotti ◽  
Hamidreza M. Nick
Keyword(s):  
Fractured Rocks ◽  
Critical Stress ◽  
Distribution Models ◽  
Equivalent Permeability ◽  
Aperture Distribution ◽  
The Impact ◽  
Stress Criteria

scholarly journals Endemic Juniperus Montane Species Facing Extinction Risk under Climate Change in Southwest China: Integrative Approach for Conservation Assessment and Prioritization

Biology ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 63
Author(s):  
Mohammed A. Dakhil ◽  
Marwa Waseem A. Halmy ◽  
Walaa A. Hassan ◽  
Ali El-Keblawy ◽  
Kaiwen Pan ◽  
...  
Keyword(s):  
Climate Change ◽  
Potential Distribution ◽  
Extinction Risk ◽  
In Situ Conservation ◽  
Integrative Approach ◽  
Conservation Assessment ◽  
Distribution Models ◽  
Area Of Occupancy ◽  
Annual Range ◽  
The Impact

Climate change is an important driver of biodiversity loss and extinction of endemic montane species. In China, three endemic Juniperus spp. (Juniperuspingii var. pingii, J.tibetica, and J.komarovii) are threatened and subjected to the risk of extinction. This study aimed to predict the potential distribution of these three Juniperus species under climate change and dispersal scenarios, to identify critical drivers explaining their potential distributions, to assess the extinction risk by estimating the loss percentage in their area of occupancy (AOO), and to identify priority areas for their conservation in China. We used ensemble modeling to evaluate the impact of climate change and project AOO. Our results revealed that the projected AOOs followed a similar trend in the three Juniperus species, which predicted an entire loss of their suitable habitats under both climate and dispersal scenarios. Temperature annual range and isothermality were the most critical key variables explaining the potential distribution of these three Juniperus species; they contribute by 16–56.1% and 20.4–38.3%, respectively. Accounting for the use of different thresholds provides a balanced approach for species distribution models’ applications in conservation assessment when the goal is to assess potential climatic suitability in new geographical areas. Therefore, south Sichuan and north Yunnan could be considered important priority conservation areas for in situ conservation and search for unknown populations of these three Juniperus species.

scholarly journals Predicting the Future Distribution of Ara rubrogenys, an Endemic Endangered Bird Species of the Andes, Taking into Account Trophic Interactions

Diversity ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 94
Author(s):  
Alain Hambuckers ◽  
Simon de Harenne ◽  
Eberth Rocha Ledezma ◽  
Lilian Zúñiga Zeballos ◽  
Louis François
Keyword(s):  
Food Resource ◽  
Bird Species ◽  
Co2 Concentration ◽  
Distribution Models ◽  
Plant Resources ◽  
Term Survival ◽  
The Andes ◽  
Vegetation Models ◽  
Fertilizing Effect ◽  
The Impact

Species distribution models (SDMs) are commonly used with climate only to predict animal distribution changes. This approach however neglects the evolution of other components of the niche, like food resource availability. SDMs are also commonly used with plants. This also suffers limitations, notably an inability to capture the fertilizing effect of the rising CO2 concentration strengthening resilience to water stress. Alternatively, process-based dynamic vegetation models (DVMs) respond to CO2 concentration. To test the impact of the plant modelling method to model plant resources of animals, we studied the distribution of a Bolivian macaw, assuming that, under future climate, DVMs produce more conservative results than SDMs. We modelled the bird with an SDM driven by climate. For the plant, we used SDMs or a DVM. Under future climates, the macaw SDM showed increased probabilities of presence over the area of distribution and connected range extensions. For plants, SDMs did not forecast overall response. By contrast, the DVM produced increases of productivity, occupancy and diversity, also towards higher altitudes. The results offered positive perspectives for the macaw, more optimistic with the DVM than with the SDMs, than initially assumed. Nevertheless, major common threats remain, challenging the short-term survival of the macaw.

scholarly journals A comparison of Galactic electron density models using PyGEDM

2021 ◽  
Vol 38 ◽  
Author(s):  
D. C. Price ◽  
C. Flynn ◽  
A. Deller
Keyword(s):  
Electron Density ◽  
Large Scale ◽  
Galactic Halo ◽  
Application Programming Interface ◽  
Dispersion Measure ◽  
Radio Pulsars ◽  
Distribution Models ◽  
Distance Measurements ◽  
Application Programming ◽  
The Impact

Abstract Galactic electron density distribution models are crucial tools for estimating the impact of the ionised interstellar medium on the impulsive signals from radio pulsars and fast radio bursts. The two prevailing Galactic electron density models (GEDMs) are YMW16 (Yao et al. 2017, ApJ, 835, 29) and NE2001 (Cordes & Lazio 2002, arXiv e-prints, pp astro–ph/0207156). Here, we introduce a software package PyGEDM which provides a unified application programming interface for these models and the YT20 (Yamasaki & Totani 2020, ApJ, 888, 105) model of the Galactic halo. We use PyGEDM to compute all-sky maps of Galactic dispersion measure (DM) for YMW16 and NE2001 and compare the large-scale differences between the two. In general, YMW16 predicts higher DM values towards the Galactic anticentre. YMW16 predicts higher DMs at low Galactic latitudes, but NE2001 predicts higher DMs in most other directions. We identify lines of sight for which the models are most discrepant, using pulsars with independent distance measurements. YMW16 performs better on average than NE2001, but both models show significant outliers. We suggest that future campaigns to determine pulsar distances should focus on targets where the models show large discrepancies, so future models can use those measurements to better estimate distances along those line of sight. We also suggest that the Galactic halo should be considered as a component in future GEDMs, to avoid overestimating the Galactic DM contribution for extragalactic sources such as FRBs.

scholarly journals Modelling Acacia saligna invasion on the Adriatic coastal landscape: An integrative approach using LTER data

2019 ◽  
Vol 34 ◽  
pp. 127-144 ◽  
Author(s):  
Flavio Marzialetti ◽  
Manuele Bazzichetto ◽  
Silvia Giulio ◽  
Alicia T.R. Acosta ◽  
Angela Stanisci ◽  
...  
Keyword(s):  
Propagule Pressure ◽  
Vascular Plant ◽  
Central Italy ◽  
Coastal Dunes ◽  
Cost Effective ◽  
Theory And Practice ◽  
Integrative Approach ◽  
Distribution Models ◽  
Adriatic Coast ◽  
The Impact

Invasive Alien Species (IAS) pose a major threat to biodiversity and ecosystem services worldwide. Even if preventing biological invasions should be the most cost-effective way to minimise the impact of IAS on biodiversity, new efforts are necessary to identify early signs of invasion and to assess invasion risk. In this context, the implementation of invasive Species Distribution Models (iSDMs) could represent a sound instrument that merits further research. Acaciasaligna is an Australian vascular plant introduced into Europe during the last half century and is one of the most aggressive IAS in the Mediterranean basin. In this work, we model the occurrence of A.saligna in the coastal landscapes of central Italy (Adriatic coast) while accounting for the simultaneous effect of multiple factors (propagule pressure, abiotic, biotic factors). The iSDM for A.saligna was implemented on a representative tract of the Adriatic coast in central Italy (Molise region), largely included in two Long-Term Ecological Research (LTER) sites which actively contribute to the description of the considered ecosystem status and possible future trends. By using a Generalised Linear Model (GLM) with a binomial distribution of errors based on field and cartographic geo-referenced data, we examined the statistical relationship between the occurrence of A.saligna and a comprehensive set of environmental factors. The iSDM effectively captured the role of the different variables in determining the occurrence of A.saligna in the coastal dunes. Its occurrence is primarily related to Wooded dunes with Pinuspinea and/or P.pinaster (EU Habitat 2270) and distance from the sea and, to a lesser extent, with distance from roads and rivers. This research provides a first exploratory analysis of the environmental characteristics that promote the rapid growth and development of A.saligna in Italian dune ecosystems, identifying the habitats that are mainly affected by the invasive process in coastal areas and, by doing so, contributing to filling the gap between theory and practice in conservation decision-making. Finally, the LTER network benefitted from this research, confirming its relevance in providing useful information for modelling and monitoring invasion processes.

scholarly journals Evaluating Stochastic Precipitation Generators for Climate Change Impact Studies of New York City’s Primary Water Supply

2017 ◽  
Vol 18 (3) ◽  
pp. 879-896 ◽  
Author(s):  
Nachiketa Acharya ◽  
Allan Frei ◽  
Jie Chen ◽  
Leslie DeCristofaro ◽  
Emmet M. Owens
Keyword(s):  
Climate Change ◽  
New York ◽  
Markov Chain ◽  
Water Supply ◽  
New York State ◽  
Distribution Models ◽  
Adaptation Studies ◽  
Precipitation Occurrence ◽  
Extreme Precipitation Events ◽  
The Impact

Abstract Watersheds located in the Catskill Mountains of southeastern New York State contribute about 90% of the water to the New York City water supply system. Recent studies show that this region is experiencing increasing trends in total precipitation and extreme precipitation events. To assess the impact of this and other possible climatic changes on the water supply, there is a need to develop future climate scenarios that can be used as input to hydrological and reservoir models. Recently, stochastic weather generators (SWGs) have been used in climate change adaptation studies because of their ability to produce synthetic weather time series. This study examines the performance of a set of SWGs with varying levels of complexity to simulate daily precipitation characteristics, with a focus on extreme events. To generate precipitation occurrence, three Markov chain models (first, second, and third orders) were evaluated in terms of simulating average and extreme wet days and dry/wet spell lengths. For precipitation magnitude, seven models were investigated, including five parametric distributions, one resampling technique, and a polynomial-based curve fitting technique. The methodology applied here to evaluate SWGs combines several different types of metrics that are not typically combined in a single analysis. It is found that the first-order Markov chain performs as well as higher orders for simulating precipitation occurrence, and two parametric distribution models (skewed normal and mixed exponential) are deemed best for simulating precipitation magnitudes. The specific models that were found to be most applicable to the region may be valuable in bottom-up vulnerability studies for the watershed, as well as for other nearby basins.

Thermophysical reservoir properties of the Hauptdolomit-facies underneath the Viennese basin across fault zones analogues – a reservoir study for the GeoTief EXPLORE project

2020 ◽  
Author(s):  
Doris Rupprecht ◽  
Sven Fuchs ◽  
Andrea Förster ◽  
Mariella Penz-Wolfmayr
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Fractured Rocks ◽  
Damage Zone ◽  
Fault Zones ◽  
Rock Properties ◽  
Zone Model ◽  
Geothermal Resources ◽  
Fault Rocks ◽  
The Impact

<p>The GeoTief EXPLORE project aims to explore the geothermal potential and quantify the geothermal resources of the Vienna Basin (Austria) and the underlying Northern Calcareous Alpine basement. The main target of geothermal interest is the massive and tectonically remolded Hauptdolomite facies that has been identified as potential geothermal reservoir in previous studies. Now, this formation is studied using outcrop analogues for the investigation of their petrophysical characterization and specific thermal properties (thermal conductivity and thermal diffusivity).</p><p> </p><p>Here, we report new measurements on a total of 60 samples from 6 outcrops in and around the area of Vienna applying different methods for the laboratory measurement of thermal and hydraulic rock properties. The petrophysical analysis considers the impact of deformation along and across fault zones, which introduces heterogeneity of storage properties and consequently in the thermophysical properties. Using the standard fault core and damage zone model, outcrop samples were grouped into unfractured and fractured protoliths, as well as in fault rocks, like breccias and cataclasites. Rock samples are then classified by their fracture density (m² fracture surface per m³ rock) and by their matrix content and differences in grain sizes, respectively.</p><p> </p><p>The measured thermal rock properties vary significantly between the selected rock groups. The total range [90 % of values] is between 3.2 and 5.0 W/(mK) for thermal conductivity and between 1.3 and 2.7 mm²/s for thermal diffusivity. The results generally met the expected trend for fractured rocks as conductivity and diffusivity decreases with increasing porosity under unsaturated and saturated conditions. The total porosities are less than 5%. The variability of thermal conductivity under saturated conditions shows complex trends depending on the different rock classifications where fault rocks and highly fractured rocks of the damage zone show lower increase in thermal conductivities.</p><p> </p><p>The new petrophysical characterization will be the base for further numerical investigations of the hydraulic and thermal regime as well as for the analysis of the geothermal resources of the Hauptdolomite.</p><p> </p><p> </p><p> </p><p> </p>

scholarly journals Study on Non-Darcian Flow in Interlayer Shear Weakness Zones in the Basalt by High-Pressure Packer Tests

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Qi Shen ◽  
Zhifang Zhou ◽  
Meng Chen ◽  
Zhe Wang ◽  
Yabing Li
Keyword(s):  
High Pressure ◽  
Darcy Law ◽  
Hydropower Station ◽  
In Situ Tests ◽  
Equivalent Permeability ◽  
Permeability Coefficients ◽  
Interlayer Shear ◽  
Baihetan Hydropower Station ◽  
Stratified Rock ◽  
The Impact

The interlayer shear weakness zone (ISWZ) is a special structural plane with different widths and spacing in stratified rock masses, it has higher permeability compared with surrounding rocks which is a risk factor for the safety of the hydropower station project. The high-pressure packer test (HPPT) by step injection is always applied to characterize the permeability of ISWZ. However, the non-Darcian flow is easy to appear under high pressure, which makes the Darcy law model no longer applicable. In this study, two non-Darcian flow analytical methods for confined aquifer were proposed to investigate the non-Darcian flow permeability parameters. The equivalent permeability coefficients of different non-Darcian models were derived as well. The in situ tests were conducted on the ISWZs at the Baihetan hydropower station to verify the proposed methods. The results indicate that the flow is non-Darcian flow in the test section from integrity to destruction during the whole HPPT process. Izbash’s law has a better fit than Forchheimer’s law in this complicated test situation. The equivalent permeability coefficients after destruction are one or two orders of magnitude larger than those before. Meanwhile, it is necessary to pay attention to the increased difference of two expressions of the equivalent permeability coefficients under higher gradient (i) or velocity (v). In general, these methods can be used to evaluate the characteristic of ISWZ to analyze the impact on engineering stability.

Basal Area and Diameter Distribution Models for Loblolly Pine Plantations with Hardwood Competition in the Piedmont and Upper Coastal Plain

1992 ◽  
Vol 16 (2) ◽  
pp. 93-98 ◽  
Author(s):  
Steven A. Knowe
Keyword(s):  
Pinus Taeda ◽  
Loblolly Pine ◽  
Coastal Plain ◽  
Basal Area ◽  
Simulation Models ◽  
Diameter Distribution ◽  
Distribution Models ◽  
Pinus Taeda L ◽  
The Impact ◽  
Volume Equations

Abstract Prediction equations were developed for basal area and percentiles of diameter distributions to account for the hardwood component in site-prepared, Piedmont and Upper Coastal Plain loblolly pine (Pinus taeda L.) plantations. Unlike existing stand-level simulation models that incorporate hardwood competition, the new equations resulted in constant total basal area regardless of the amount of hardwood competition and permitted the variance of the diameter distribution to increase with increasing proportion of hardwoods. The equations presented can be used with existing dominant height, survival, and volume equations as a tool for assessing the impact of hardwoods on loblolly pine yield. South. J. Appl. For. 16(2):93-98.

scholarly journals Stability of nanobeams and nanoplates with defects

2021 ◽  
Vol 25 (2) ◽  
pp. 221-238
Author(s):  
Hina Arif ◽  
Jaan Lellep
Keyword(s):  
Critical Stress ◽  
Nonlocal Theory ◽  
Theory Of Elasticity ◽  
Buckling Load ◽  
Physical Parameters ◽  
Axial Loads ◽  
Critical Buckling Load ◽  
Support Conditions ◽  
The Impact

The sensitivity of critical buckling load and critical stress concerning different geometrical and physical parameters of Euler-Bernoulli nanobeams with defects is studied. Eringen’s nonlocal theory of elasticity is used for the determination of critical buckling load for stepped nanobeams subjected to axial loads for different support conditions. An analytical approach to study the impact of discontinuities and boundary conditions on the critical buckling load and critical stress of nanobeams has been developed. Critical buckling loads of stepped nanobeams are defined under the condition that the nanoelements are weakened with stable crack-like defects. Simply supported, clamped and cantilever nanobeams with steps and cracks are investigated in this article. The presented results are compared with the other available results and are found to be in a close agreement.

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