Numerical modelling of impact cratering has reached a high degree of sophistication; however, the treatment of porous materials still poses a large problem in hydrocode calculations. We present a ...novel approach for dealing with porous compaction in numerical modelling of impact crater formation. In contrast to previous attempts (e.g., P-alpha model, snowplow model), our model accounts for the collapse of pore space by assuming that the compaction function depends upon volumetric strain rather than pressure. Our new
ɛ-alpha model requires only four input parameters and each has a physical meaning. The model is simple and intuitive and shows good agreement with a wide variety of experimental data, ranging from static compaction tests to highly dynamic impact experiments. Our major objective in developing the model is to investigate the effect of porosity and internal friction on transient crater formation. We present preliminary numerical model results that suggest that both porosity and internal friction play an important role in limiting crater growth over a large range in gravity-scaled source size.
China’s Belt and Road Initiative (BRI) is the largest infrastructure scheme in our lifetime, bringing unprecedented geopolitical and economic shifts far larger than previous rising powers. Concerns ...about its environmental impacts are legitimate and threaten to thwart China’s ambitions, especially since there is little precedent for analysing and planning for environmental impacts of massive infrastructure development at the scale of BRI. In this paper, we review infrastructure development under BRI to characterise the nature and types of environmental impacts and demonstrate how social, economic and political factors can shape these impacts. We first address the ambiguity around how BRI is defined. Then we describe our interdisciplinary framework for considering the nature of its environmental impacts, showing how impacts interact and aggregate across multiple spatiotemporal scales creating cumulative impacts. We also propose a typology of BRI infrastructure, and describe how economic and socio-political drivers influence BRI infrastructure and the nature of its environmental impacts. Increasingly, environmental policies associated with BRI are being designed and implemented, although there are concerns about how these will translate effectively into practice. Planning and addressing environmental issues associated with the BRI is immensely complex and multi-scaled. Understanding BRI and its environment impacts is the first step for China and countries along the routes to ensure the assumed positive socio-economic impacts associated with BRI are sustainable.
Global warming is attracting a growing interest worldwide for the generation of large-scale energy from renewable energy sources as it is free from greenhouse gas emissions. Wind energy is one of the ...most promising renewable energy sources due to its availability and low cost and due to the fact that it is more efficient and advanced in technology. Hence, harvesting of large-scale wind energy is of prime interest today. However, large-scale integration of wind energy sources creates environmental, economic, social and technical impacts that need to be investigated and mitigated as part of developing a sustainable power system for the future. Government, utilities and research communities are working together to increase penetration of wind energy into the power grid and overcome potential barriers associated with this. This paper presents an extensive and useful survey on wind energy technology and associated implementation issues including effects of wind farms on the nearby locality. This paper also reviews the social, environmental and cost-economic impacts of installing large-scale wind energy plants. Finally, potential technical challenges to the integration of large-scale wind energy into the power grid are reviewed in regard to current research with their available mitigation techniques.
Increasing concentrations of greenhouse gases in the atmosphere are expected to modify the global water cycle with significant consequences for terrestrial hydrology. We assess the impact of climate ...change on hydrological droughts in a multimodel experiment including seven global impact models (GIMs) driven by bias-corrected climate from five global climate models under four representative concentration pathways (RCPs). Drought severity is defined as the fraction of land under drought conditions. Results show a likely increase in the global severity of hydrological drought at the end of the 21st century, with systematically greater increases for RCPs describing stronger radiative forcings. Under RCP8.5, droughts exceeding 40% of analyzed land area are projected by nearly half of the simulations. This increase in drought severity has a strong signal-to-noise ratio at the global scale, and Southern Europe, the Middle East, the Southeast United States, Chile, and South West Australia are identified as possible hotspots for future water security issues. The uncertainty due to GIMs is greater than that from global climate models, particularly if including a GIM that accounts for the dynamic response of plants to CO ₂ and climate, as this model simulates little or no increase in drought frequency. Our study demonstrates that different representations of terrestrial water-cycle processes in GIMs are responsible for a much larger uncertainty in the response of hydrological drought to climate change than previously thought. When assessing the impact of climate change on hydrology, it is therefore critical to consider a diverse range of GIMs to better capture the uncertainty.
The concept of green building has gradually formed with the increase in public awareness of environmental protection, which also covers a wide range of elements. The green building is the fundamental ...platform of sustainable development. This review paper provides solutions for the multi-dimensional and balanced development of green building. Since green building is the development trend of the construction industry, it presents an opportunity to mitigate global warming and accomplish energy efficiency. However, the problem is that the development of green building’s implementation is restricted by the lack of government policies, imperfect technical abilities and unreasonable economic benefits. One conclusion drawn from the results shows that the benefits of green building implementation include environmental, economic, social, and health and safety aspects. Moreover, it is crucial to improve the awareness of stakeholders to promote the development process of green building. The government should launch campaigns to encourage developers and tenants to embrace green building, which can add value to buildings. The novelty of the paper provides a more systematic review on the sustainable considerations of green building than previous efforts in the literature. Bibliometric analysis is conducted through VOS viewer software. This review paperdiscusses the relevant benefits and challenges of green building through a critical review of existing research knowledge related to green building. The current advancements in green building are highlighted in this paper. Importantly, future recommendations for standards and policy formulation and future research directions are proposed in this review article.
As of 2023, 188 non-native species have been identified in the Laurentian Great Lakes, with about half being considered benign. Some of these species have been elevated to the status of invasive ...(i.e. causing extreme negative effects). Here, we identified and quantitatively ranked in order of impact (highest to lowest), the top ten aquatic nonindigenous species (ANS) determined to have the most significant negative environmental and socio-economic effects. To accomplish this, we used an organism impact assessment (OIA) tool developed by the Great Lakes Aquatic Nonindigenous Species Information System (GLANSIS). The top ten identified species included: zebra mussel (Dreissena polymorpha); quagga mussel (Dreissena bugensis); alewife (Alosa pseudoharengus); sea lamprey (Petromyzon marinus); Japanese stiltgrass (Microstegium vimineum); grass carp (Ctenopharyngodon idella); water chestnut (Trapa natans); common reed (Phragmites australis australis); round goby (Neogobius melanostomus); and white perch (Morone americana). The taxonomic groupings, continent of origin, and vectors of introduction of these top ten invaders do not reflect the full diversity of all invasive species in the Great Lakes region. The most common shared negative effects were: direct hazards or threats posed to native species, alteration of predator/prey dynamics, aggressive competition with native species, and costly damage to human recreation, aesthetics, and economic activities. These quantitative rankings of the top ten most harmful ANS can serve as a reference point for researchers, educators and communicators as the Great Lakes continue to be affected by the spread of invasive species and other contemporary and future anthropogenic factors affecting the Great Lakes ecosystem.
Impact cratering is an important geological process on Earth. This review summarizes the state of knowledge of the Precambrian (Hadean, Archean, and Proterozoic) impact record on Earth. After an ...early collision that may have led to the formation of the Moon, both Earth and Moon suffered intense post-accretionary bombardment at about 4.5 and 3.9 billion years ago. Evidence for a “late heavy bombardment” phase at about 3.85 Ga is currently debated because the lunar rock record might be biased, and no relevant impact record has yet been confirmed on Earth. Several 3.5 to 2.5 Ga old spherule layers in South Africa and Australia, and two large impact structures, Vredefort and Sudbury, at about 2 Ga, represent most of the oldest actual terrestrial impact record. The impact record for more than half of the geological history of the Earth is incomplete, and, as a result of the lack of old continental crust on Earth, there is also only limited evidence for impact processes during the first 2.5 billion years of Earth history. Some more (mostly badly dated) impact structures are (partly) preserved for the Proterozoic period, as are a couple of ejecta layers. Given that the rock record preserved on Earth is very restricted for this early time period, the limited impact record is not surprising, but as recent discoveries show, there is still room for more research and new findings.
Tektites contain inclusions of lechatelierite, nearly pure SiO2 glass formed by quenching of quartz grains melted during hypervelocity impacts. We report the discovery in a tektite of chemically ...zoned boundary layers (ca 20 μm) between lechatelierite and host felsic glass. These boundary layers in tektites formed by chemical diffusion between molten silica inclusions (quenched to lechatelierite on cooling) and surrounding felsic melt. We reproduced the details of these boundary layers via experiments on mixtures of powdered natural tektite plus quartz grains heated to 1800–2400 °C for 1–120 s using an aerodynamic levitation laser heating furnace. The results of these experiments were used to provide quantitative constraints on possible thermal histories of the natural sample.
The experiments successfully reproduced all major aspects of the concentration profiles from the natural sample including diffusion length scale, strong asymmetry of the concentration profiles with respect to the Matano plane (due to the strong concentration dependence of the diffusivities of all oxides on SiO2 content), similarities in lengths of the diffusive profiles (due to control by the diffusion of SiO2 on the diffusivity of the other oxides), and differences in the shapes of the profiles among the oxides (including a maximum in the diffusion profile of K2O due to uphill diffusion). The characteristic lengths of all non-alkali oxide profiles are proportional to t from which diffusivities and activation energies can be derived; these results are consistent with measurements in melts with lower SiO2 contents and at lower temperatures reported in the literature. We also fit the experimental profiles of SiO2 and Al2O3 using simple formulations of the dependence of their diffusivities on SiO2 content and temperature, yielding results similar to those obtained from the t dependence of the characteristic profile lengths.
The quantitative characterization of diffusion in boundary layers based on our experiments allow us to set limits on the thermal history of the natural tektite in which the boundary layers were discovered. If the interdiffusion between the silica and felsic melts occurred at constant temperature, the duration of heating experienced by the natural tektite we studied depends on temperature; possible solutions include heating at ∼2000 °C for ∼70 s, −2400 °C for ∼3 s. We also explored non-isothermal, asymptotic cooling histories; for a maximum temperature of 2400 °C, a characteristic cooling time scale of ∼50 s is implied, whereas, for 2000 °C, the time scale is ∼1400 s. Further, a maximum temperature of ∼2360 °C yields an effective diffusive time scale of ∼5 s, a cooling time scale of ∼90 s, and a cooling rate at the glass transition temperature of ∼5 °C/s; results that are consistent with independent estimates of cooling time scales for ∼1 cm clasts (Xu and Zhang, 2002), as well as cooling rates at the glass transition temperature (Wilding et al., 1996) – thus satisfying all currently available relevant data. More complex T-t paths are possible and can also be modeled using our experimental results and compared with and used as tests of the accuracy of physical models of tektite-forming impact events.
The potential links between climate and conflict are well studied, yet disagreement about the specific mechanisms and their significance for societies persists. Here, we build on assessment of the ...relationship between climate and organized armed conflict to define crosscutting priorities for future directions of research. They include (1) deepening insight into climate‐conflict linkages and conditions under which they manifest, (2) ambitiously integrating research designs, (3) systematically exploring future risks and response options, responsive to ongoing decision‐making, and (4) evaluating the effectiveness of interventions to manage climate‐conflict links. The implications of this expanding scientific domain unfold in real time.
Key Points
Disagreement about the relationship between climate and the risk of violent conflict persists, limiting societal management of the risks
Future directions for climate‐conflict research include deepening insight on what the links are, when they matter, and how they manifest
Compelling opportunities necessitate integrating research designs, responsive to ongoing decision‐making and potential responses
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