Hasil untuk "Geology"

F. J. Flanagan

P. Green, I. Duddy, G. Laslett et al.

D. D. Groot

C. S. Hutchison

Qiujie MENG, Yixiang SONG, Da HUANG et al.

The sensitivity of the ice-water transition in glacial debris to temperature rise has become a significant concern. In recent years, there has been an increase in reports of ice avalanches caused by the thawing of glacial debris, which can be attributed to the impact of global warming. To study the temperature-dependent degradation of shear strength in glacial debris, a Finite Discrete Element Model (F-DEM) was developed. This model consists of solid permafrost and gravel elements and cohesive elements, as well as cohesive elements. The strength degradation law of the glacial debris, as observed in tests, is described as a strength degradation process of the cohesive elements. Initially, cohesive elements using the “traction-separation” criterion are set in between solid elements to represent interstitial ice. Subsequently, a strength degradation law governing the degradation law is implemented through the development of the VUSDFLD subroutine in Abaqus. The strength degradation of the cohesive elements is controlled by temperature field variables. The macroscopic numerical results obtained from the simulation were compared to experimental results. The simulated shear characteristics, including peak shear strength, deformation mode, and failure mode closely matched the experimental findings. The influence of three different factors, namely the thawing rate, gravel content, and stress magnitude on shear behavior was investigated. When the thawing rate is less than or equal to 2%, the failure mode exhibits a rough “serrated” pattern; as the thawing rate increases (> 2%), the shear surface gradually transitions to a smoother “circular arc” shape. The significant difference in strength at the permafrost-gravel interface can easily lead to stress concentration, resulting in cracks propagating along the interface. Increasing gravel content leads to a decrease in the shear strength of glacial debris, and the sensitivity of the shear strength to gravel content decreases with increasing thawing ratio. Under high shear loading, even a slight increase in temperature can cause sudden changes in shear strain. The deformation under constant load can be divided into three stages: the initial stage, the developmental stage, and the rapid deformation stage. In the initial stage, shear strain initially increases and then stabilizes; and during the developmental stage, there is a critical point in strain; during the rapid deformation stage, shear strain increases rapidly. The temperature of the critical point decreases with an increase in initial shear stress, and they are approximately linearly related. At higher shear stress levels, the shear strain of glacial debris is highly sensitive to temperature changes. Further studies should be conducted on model simplification, variation laws of parameters, phase transitions, and size effects to better simulate the shear strength degradation behavior under actual glaciers.

Aravind Bodakunta

Abstract This paper presents a case study on the digital transformation of the Timber Buyers Program within the Illinois Department of Natural Resources (IDNR). The initiative replaced outdated, paper-based systems for timber buyer licensing and harvest fee tracking with a modern, GIS-integrated web ap- plication. This transformation not only improved operational efficiency and significantly boosted harvest fee revenue, but also established a strategic roadmap to strengthen enforcement against illegal timber activities, directly supporting the efforts of District Forest Officers and Conservation Police Officers. By integrating ArcGIS, the solution enabled precise geolocation of timber harvest sites—a capability previously unavailable to the agency. The case highlights how the strategic application of geospatial and IT expertise can deliver measurable improvements in public-sector forest management, offering a scalable model for environmental conservation agencies across the United States. The study adopts a mixed-method approach, combining spatial analysis and operational data from 2023 to 2024 to evaluate the measurable impact of GIS integration on efficiency and revenue. Quantitative validation demonstrates improved data accuracy and enforcement outcomes, reinforcing the significance of GIS as an evidence-based governance tool.

Fang Liu, Hongbo Zhang, Yihang Li et al.

Study region: This study focuses on the Wuding River Basin, located in the middle reaches of the Yellow River Basin in China. Study focus: Event Synchronization (ES) and Event Coincidence Analysis (ECA) were used to investigate the spatiotemporal co-evolution of the multi type of meteorological variable drought (SIMVs) and SSMI in the basin, including the precursor and triggering effect of SIMVs on agricultural drought and the occurrence and development of different levels of agricultural drought events under meteorological variable disturbance. New hydrological insights for the region: In the precursor-and-trigger analysis of ECA, SWI was the main precursor and trigger factor for mild agricultural drought and SPI for moderate and severe drought. The precursor coincidence rate is higher than the trigger coincidence rate, suggesting that not all precursory SIMV events cause agricultural drought. All precursory and triggering effects diminish as the observation time window rises, demonstrating that SIMV has a bigger impact on low-grade agricultural drought. SPI caused 26.86 % of agricultural drought, whereas coupled SIMVs triggered it. The synchronization analysis shows that the lag times for SPI, STI, SWI, and SNR early warnings of drought are 65.7 days, 60.5 days, 52.8 days, and 55.8 days, respectively. The lag times for SIMV triggers are 61.8 days, 53.7 days, 48.4 days, and 53 days.

Beatriz Silva Fernandes, Stefania Cristino de Oliveira, Fabiano N. Pupim

Land use changes and dam construction have impacted sediment yield in river catchments worldwide. This is especially true in central-west Brazil, where most of the main watersheds have been deforested and rivers, such as the Cuiabá, have been dammed in the last 50 years. Here, we investigated the geomorphological and sedimentary responses of the Cuiabá River to land use changes and dams since 1985, using a time-series of Landsat images to quantify fluvial bars, channel width, channel migration rate and suspended sediment concentration (SSC). Our results showed an increase in the area occupied by fluvial bars and in SSC between 1985 and 2000, driven by natural vegetation conversion to agriculture. However, construction of the Manso Dam in 2000 led to a decrease in bar area, migration rates and SCC downstream. The SSC time-series also showed that sediment production remains high up to the present day in the monitoring section upstream of the Manso Dam, triggered by new waves of deforestation since the early 2000s. We conclude that land cover change led to increased sediment supply to the Cuiabá River, especially before the 2000s. However, this effect was surpassed by dam constructions in the watershed, which drove a significant decrease in sediments exported downstream.

R. Larson

D. Stanley, A. Warne

Andrew H. Knoll

Na WANG, Lei WU, Jiasong WANG et al.

Optically stimulated luminescence (OSL) dating includes the measurement of the equivalent dose and the environmental dose rate. The accurate determination of uranium, thorium and potassium is an important step in ensuring the accurate calculation of the environmental dose rate. The commonly used measurement method is the combination of inductively coupled plasma-mass spectrometry/optical emission spectroscopy (ICP-MS/OES), but the determination of uranium, thorium and potassium can not be done at the same time, and the measurement time is long. In the research, two methods of ICP-MS and X-ray fluorescence spectrometry (XRF) measuring the three elements were compared. Using ICP-MS analysis, electronic dilution was used to reduce the potassium ions entering the detector, so that potassium ions were in the same order of magnitude as uranium and thorium ions. Thus, the simultaneous analysis of high content potassium and low content uranium and thorium was achieved. The detection limits for uranium, thorium, and potassium were 6.38ng/L, 8.52ng/L, and 926ng/L, respectively. The effects of closed acid dissolution method and open acid dissolution method on the determination of uranium, thorium, and potassium by ICP-MS method were studied. The two dissolution methods dissolved 10 sediment and soil standard substances, and the results of uranium, thorium, and potassium determination were accurate and reliable, with no significant difference in relative error, ranging from 0 to 9.33%. However, the operation of open acid dissolution method was simpler, and the sample processing time (about 9h) was much shorter than the closed acid dissolution method (about 60h). Therefore, open acid dissolution was selected to dissolve the sample in ICP-MS method. By XRF analysis, the relative errors for the determination of uranium, thorium and potassium in standard materials by pressed-powder pellets method were 4.78%−16.2%, 1.20%−13.3% and 0.00%−5.67%, respectively. ICP-MS and XRF were used to determine 20 sediment samples from Bohai Bay, and the relative deviation of the environmental dose rate was less than 6%. XRF has advantages in the measurement of potassium and is more suitable for luminescent samples with high potassium content. The ICP-MS method has a lower detection limit, and higher precision and accuracy for the determination of uranium and thorium. For ultra trace samples, this method provides more accurate measurement results.

Chao Xu, Wen Wang, Yanjun Hu et al.

Study region: China. Study focus: Accurate estimation of potential evapotranspiration (PET) is essential for understanding climate change. Using ground-based pan evaporation measurements over continental China, the monthly scale PET data during 2000–2017 of ERA5, ERA5-Land, GLDAS-2.1/Noah, and GLEAM V3.8a are evaluated, from the perspectives of their consistency in spatiotemporal variation, and performance measures. Factors controlling the data quality of the four datasets are investigated from the perspective of their PET calculation models and meteorologically input data. New hydrological insights for the region: PETERA5 performs the best in mainland China among four gridded PET datasets with higher correlation coefficients (r) and smaller biases, which can well capture the temporal variation of Epan. The outstanding performance of PETERA5 in China mainly results from the utilization of the Penman-Monteith (P-M) equation which performs the best among several competing formulas for PET computation, as well as its better meteorological inputs for computing PET than other datasets. Although the PETERA5-Land is a replay of the land component of the ERA5 climate reanalysis, it exhibits substantial overestimation of PET values and temporal trends, particularly in coastal areas of Southern China and the eastern side of Northeastern China, mainly caused by the overestimation of its net radiation. The PETGLDAS shows significant overestimation, partly due to its overestimation of wind speed, but mostly due to its modified P-M equation with its parameterization of land surface conditions for computing PETGLDAS. The PETGLEAM underestimated PET generally mainly due to the joint effect of the use of the Priestley-Taylor equation with small P-T parameter α, and the underestimation of the net radiation input from ERA-Interim, especially in Northwest and Qinghai Tibet.

Mohammad Siami, Tomasz Barszcz, Jacek Wodecki et al.

Abstract The belt conveyor (BC) is the main means of horizontal transportation of bulk materials at mining sites. The sudden fault in BC modules may cause unexpected stops in production lines. With the increasing number of applications of inspection mobile robots in condition monitoring (CM) of industrial infrastructure in hazardous environments, in this article we introduce an image processing pipeline for automatic segmentation of thermal defects in thermal images captured from BC idlers using a mobile robot. This study follows the fact that CM of idler temperature is an important task for preventing sudden breakdowns in BC system networks. We compared the performance of three different types of U-Net-based convolutional neural network architectures for the identification of thermal anomalies using a small number of hand-labeled thermal images. Experiments on the test data set showed that the attention residual U-Net with binary cross entropy as the loss function handled the semantic segmentation problem better than our previous research and other studied U-Net variations.

J. Dixon, A. Robertson

S. Gilfillan, B. Lollar, G. Holland et al.

R. Hall, J. Holloway

M. Salvatores, G. Palmiotti

W. B. Solley, R. R. Pierce, H. Perlman

Zhiye Wang, Chuanming Ma, Yan Zhang et al.

Expanding urbanization has led to an increased risk of urban flooding, which poses a hazard to humans. Scientific assessment of urban flooding vulnerability (UFV) is essential to protect human health and reduce losses. In this study, UFV was assessed using the Analytic Hierarchy Process-Press-State-Response (AHP-PSR) model in Jining City, China. The urban flooding index (UFI) was calculated from 13 indicators. Based on the magnitude of UFI, the vulnerability was classified into five classes. Among them, the areas of very high, high, medium, low and very low vulnerability are 897.21 km2 (8.02%), 3192.14 km2 (28.53%), 2063.22 km2 (18.44%), 39773.96 km2 (35.52%) and 1060.47 km2 (9.48%), respectively. Finally, suggestions were proposed for further urban flooding management based on the results. The results of the study can provide an important reference for the government to prevent and mitigate urban flooding. Meanwhile, the modeling framework can be easily transferred to other cities, providing new ideas for UFV assessment.