bluuebunny/crossref_metadata_2025 huggingface dataset:
SARS-CoV-2 infection predicts larger infarct volume in patients with acute ischemic stroke
Authors: De Michele Manuela , Lorenzano Svetlana , Piscopo Paola , Rivabene Roberto , Crestini Alessio , Chistolini Antonio , Stefanini Lucia , Pulcinelli Fabio M. , Berto Irene , Campagna Roberta , Amisano Paolo , Iacobucci Marta , Cirelli Carlo , Falcou Anne , Nicolini Ettore , Schiavo Oscar G. , Toni Danilo
Published: January 2023

Background and purpose

Acute ischemic stroke (AIS) is a fearful complication of Coronavirus Disease-2019 (COVID-19). Aims of this study were to compare clinical/radiological characteristics, endothelial and coagulation dysfunction between acute ischemic stroke (AIS) patients with and without COVID-19 and to investigate if and how the SARS-CoV-2 spike protein (SP) was implicated in triggering platelet activation.

Methods

We enrolled AIS patients with COVID-19 within 12 h from onset and compared them with an age- and sex-matched cohort of AIS controls without COVID-19. Neuroimaging studies were performed within 24 h. Blood samples were collected in a subset of 10 patients.

Results

Of 39 AIS patients, 22 had COVID-19 and 17 did not. Admission levels of Factor VIII and von Willebrand factor antigen were significantly higher in COVID-19 patients and positively correlated with the infarct volume. In multivariate linear regression analyses, COVID-19 was an independent predictor of infarct volume (B 20.318, Beta 0.576, 95%CI 6.077–34.559; p = 0.011). SP was found in serum of 2 of the 10 examined COVID-19 patients. Platelets from healthy donors showed a similar degree of procoagulant activation induced by COVID-19 and non-COVID-19 patients' sera. The anti-SP and anti-FcγRIIA blocking antibodies had no effect in modulating platelet activity in both groups.

Conclusions

SARS-CoV-2 infection seems to play a major role in endothelium activation and infarct volume extension during AIS.
The proGnostic role of caRdiac rehAbilitation in patients with left ventriCular anEurysm formation after anterior myocardial infarction (the GRACE study): Study rationale and design of a prospective randomized controlled trial
Authors: Zhang Peng , Ge Xiaofeng , Li Zhaokai , Nie Meiling , Yu Jing , Ou Weimei , Wu Kaimin , Li Jiahua , Wang Lin , Ni Wei , Shi Zaixing , Song Juan , Li Suiji , Dai Cuilian
Published: January 2023

Background

Cardiac rehabilitation (CR) is an essential intervention after acute myocardial infarction (MI). However, it is still unclear whether patients with left ventricular aneurysm (LVA) formation after anterior MI would benefit from CR programs. This clinical trial is designed to assess the role of CR in patients with LVA formation after anterior MI.

Trial design

The GRACE study is a single-center, single-blind, prospective, randomized controlled clinical trial in China. 100 subjects aged 18–75 years with LVA formation after anterior MI will be recruited and randomized 1:1 to the CR or control group. Both groups will receive standard drug treatment and routine health education according to the guidelines. Participants in the CR group will additionally receive tailored CR programs delivered over a period of 36 sessions. These participants will then be followed up for 1-year. The primary outcome is peak oxygen uptake measured by cardiopulmonary exercise testing after CR programs. The secondary outcomes are cardiac function and EuroQol 5-Dimension-3 Level index scores after CR program and 1-year and major adverse cardiac cerebrovascular events, a composite of cardiovascular mortality, non-fatal MI, non-fatal stroke, malignant arrhythmia or hospitalization for heart failure during the follow-up period.

Conclusions

This single-center, single-blind, prospective, randomized controlled clinical trial will determine whether CR improves physical capacity and clinical outcomes in patients with LVA formation after anterior MI.

Trial registration

Chinese Clinical Trial Registry ChiCTR2200058852. Registered on 18 April 2022.
Audio deepfakes: A survey
Authors: Khanjani Zahra , Watson Gabrielle , Janeja Vandana P.
Published: January 2023

A deepfake is content or material that is synthetically generated or manipulated using artificial intelligence (AI) methods, to be passed off as real and can include audio, video, image, and text synthesis. The key difference between manual editing and deepfakes is that deepfakes are AI generated or AI manipulated and closely resemble authentic artifacts. In some cases, deepfakes can be fabricated using AI-generated content in its entirety. Deepfakes have started to have a major impact on society with more generation mechanisms emerging everyday. This article makes a contribution in understanding the landscape of deepfakes, and their detection and generation methods. We evaluate various categories of deepfakes especially in audio. The purpose of this survey is to provide readers with a deeper understanding of (1) different deepfake categories; (2) how they could be created and detected; (3) more specifically, how audio deepfakes are created and detected in more detail, which is the main focus of this paper. We found that generative adversarial networks (GANs), convolutional neural networks (CNNs), and deep neural networks (DNNs) are common ways of creating and detecting deepfakes. In our evaluation of over 150 methods, we found that the majority of the focus is on video deepfakes, and, in particular, the generation of video deepfakes. We found that for text deepfakes, there are more generation methods but very few robust methods for detection, including fake news detection, which has become a controversial area of research because of the potential heavy overlaps with human generation of fake content. Our study reveals a clear need to research audio deepfakes and particularly detection of audio deepfakes. This survey has been conducted with a different perspective, compared to existing survey papers that mostly focus on just video and image deepfakes. This survey mainly focuses on audio deepfakes that are overlooked in most of the existing surveys. This article's most important contribution is to critically analyze and provide a unique source of audio deepfake research, mostly ranging from 2016 to 2021. To the best of our knowledge, this is the first survey focusing on audio deepfakes generation and detection in English.
Changing features of the Northern Hemisphere 500-hPa circumpolar vortex
Authors: Bushra Nazla , Rohli Robert V. , Li Chunyan , Miller Paul W. , Mostafiz Rubayet Bin
Published: January 2023

The tropospheric circumpolar vortex (CPV), an important signature of processes steering the general atmospheric circulation, surrounds each pole and is linked to the surface weather conditions. The CPV can be characterized by its area and circularity ratio (Rc), which both vary temporally. This research advances previous work identifying the daily 500-hPa Northern Hemispheric CPV (NHCPV) area, Rc, and temporal trends in its centroid by examining linear trends and periodic cycles in NHCPV area and Rc (1979–2017). Results suggest that NHCPV area has increased linearly over time. However, a more representative signal of the planetary warming may be the temporally weakening gradient which has blurred NHCPV distinctiveness—perhaps a new indicator of Arctic amplification. Rc displays opposing trends in subperiods and an insignificant overall trend. Distinct annual and semiannual cycles exist for area and Rc over all subperiods. These features of NHCPV change over time may impact surface weather/climate.
Adverse events in rheumatoid arthritis patients under antimalarial treatment—Is there cardiovascular compromise?
Authors: Santos-Moreno Pedro , Ibatá Linda , Martínez Susan , Rodríguez-Vargas Gabriel-Santiago , Villarreal Laura , Rodríguez Pedro , Rivero Wilberto , Rodríguez-Florido Fernando , Rojas-Villarraga Adriana
Published: January 2023

Introduction: The antimalarials chloroquine and hydroxychloroquine have been used for several decades in treating malaria and some autoimmune diseases—mainly rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE)—with excellent efficacy and safety. Due to the massive use of antimalarials worldwide for managing SARS-CoV-2/COVID-19 infection during the last 2 years and the consequent increase in cardiac arrhythmia, fear has risen about the safety of using antimalarials, especially for patients with increased cardiovascular risk.

Objective: To describe a real-life experience about the safety of antimalarials in the setting of a single rheumatological center in Colombia.

Methods: This is a cross sectional study that includes patients diagnosed with RA and treated with antimalarials between 2020 and 2021. Clinical follow-up information was gathered from the medical records, and all reported adverse events were described.

Results: A total of 957 patients were included, primarily women (79.2%). The most frequent comorbidities were hypertension and osteoporosis. Chloroquine use was more frequent than hydroxychloroquine (86.4% vs. 13.6%). During the observation period, 243 (25.4%) patients presented at least one adverse event, 72 (29.6%) had retinal toxicity, 85 (35%) dermatological events, and 81 (33.3%) gastrointestinal intolerance. Other adverse events reported less frequently (15.2%) included headache, dizziness, lipothymia, and elevated transaminases. There were no reports of cardiovascular events from the period of antimalarial use to the date of data collection despite the high frequency of previous metabolic or cardiovascular disease in this cohort.

Conclusion: This study reasserts the evidence of antimalarials safety profile for patients with rheumatological conditions such as RA. RA patients that were treated with antimalarials at doses recommended by the guidelines had no cardiovascular events.
Effect of construction technology on air-lifting pump mining
Authors: Zhao Yan-Lin , Wang Xia-Guang , Tang Chuan-Lin , Hu Dong , Lin Peng , Xia Mei-Li
Published: January 2023

The air-lifting pump has the advantages of low cost, strong reliability, simple structure and convenient maintenance, especially in the fields of deep-sea mining, oilfield mining and mineral mining under complex geological conditions. The construction technology and air intake mode not only play a decisive role in the performance of the air-lifting pump, but also greatly hinder the engineering application of the air-lifting pump. Here, the air-lifting pump is taken as the research object, and the river sand is used as the experimental transport medium. The particle concentration-efficiency model is established based on the mechanical energy conservation theorem. The working performance characteristic parameters of the air-lifting pump under different construction technologies are obtained by a three-axis motion control system. On this basis, the working performance characteristic parameters of the air-lifting pump under different intake modes are obtained by changing the intake mode. The results show that the particle concentration-efficiency model can well describe the efficiency of lifting solid particles by the air-lifting pump. When the sand depth is less than 200 mm, the concentration and efficiency of solid particles transported by the air-lifting pump in the horizontal movement construction are significantly better than those in the fixed position construction. In the same construction technology, the solid particle concentration of the air-lifting pump in uniform intake mode is better than that in non-uniform intake mode, while the transportation efficiency of the air-lifting pump in non-uniform intake mode is better than that in uniform intake mode. The research results of this paper can provide an important theoretical reference value for the air-lifting pump in practical engineering applications.
Law of strata pressure behavior of surrounding rock in nearby goaf roadway for extra-thick coal seams of Datong mine area
Authors: Lian Xiaoyong , Li Chen , Li Jun , Wu Liang
Published: January 2023

The nearby goaf road in the extra-thick coal seam of the Datong mining area exhibits intense strata pressure behavior, which affects the working face mining. Herein, we study the laws of the strata pressure behavior of this road in detail using various methods, including laboratory tests, theoretical analyses, numerical simulation, and field monitoring. Considering the mine pressure characteristics of the nearby goaf road, namely, roof cracking, two-side deformation, and floor heaving, the mechanical tests and theoretical failure analyses of the surrounding rock in the mining-induced non-uniform stress field were carried out. The circular-oval-butterfly failure trend of the surrounding rock in the nearby goaf road under the influence of mining was obtained. The steady failure evolution lateral pressure coefficient (λ=0.5∼1.8) and butterfly mutation lateral pressure coefficient (λ<0.35 or λ>2.1) of the surrounding rock in the nearby goaf road were analyzed. We performed numerical simulation to study the stress field and the plastic zone shape-size characteristics of the surrounding rock during excavation and mining (with or without the top extraction road), and the theoretical law of the mine pressure was obtained for the Tong Xin coal mine. Finally, field monitoring indicates that the mine pressure behavior of the nearby goaf road exhibits spatial differences, namely, the difference between the stresses of the two sides and roof, and the stress characteristics of the deep and shallow surrounding rock. The findings of this study on the mine pressure behavior in the nearby goaf road have great practical significance for targeted measures to control the surrounding rock stability.
Simulation of one-dimensional dam-break flood routing based on HEC-RAS
Authors: Mo Chongxun , Shen Yue , Lei Xingbi , Ban Huazhen , Ruan Yuli , Lai Shufeng , Cen Weiyan , Xing Zhenxiang
Published: January 2023

Dam-break is a serious disaster resulting in severe damage to downstream communities. Therefore, analyzing the affected range and the evolution process of dam-break floods in advance is valuable. However, the difficulties and challenges lie in the complexity of the breaking process of earth-rock dams, the uncertainty in the evolution of dam-break floods, and the geographical variability. Given this, the objective of this study is to analyze the characteristics of the dam-break flood evolution. The study chooses Chengbi River Reservoir as the research object, HEC-RAS as the simulation software, unsteady flow differential equations and one-dimensional Saint-Venant equations as the control equations, and it uses four-point implicit finite difference method for discrete solution. In this paper, the dam-break flood evolution is simulated under three boundary conditions (full breach, 1/2 breach, 1/3 breach), and the main results are as follows. From the dam site section to the Tianzhou hy-drological station section, the peak discharge decay rates of the three schemes are 78%, 77%, and 67%, respectively. The water level decay rates of the three schemes are 47%, 36%, and 30%, respectively. A 1 m increase in the bursting water level elevation increases the peak flow by ap-proximately 7%, and the highest water level in front of the dam by 1 m, and delays the peak time by 1.5 h on average. In addition, the preliminary inundation extent for the Baise City is obtained. The analysis results can provide a fundamental basis for flood control as well as a reference for flood disaster management.
Influence of thermochemical sulfate reduction on oxygen isotopic composition of calcite cements in carbonates of the Triassic Feixianguan and Permian Changxing formations in the Sichuan Basin, China
Authors: Wang Guangwei , Hao Fang , Zou Huayao , Li Pingping
Published: January 2023

Calcite cement is a common diagenetic mineral in carbonate rocks and plays an important role on rock quality as hydrocarbon reservoirs. Traditionally, oxygen isotopic compositions (δ18O) of the diagenetic calcites tend to decrease with increasing depths due to temperature-dependent isotope fractionation. In this study, the stable isotope compositions of the calcite cements in the Changxing and Feixianguan formations from the Puguang, Yuanba, Jiannan and Fuling carbonate fields in the Sichuan Basin were analyzed. The results show that some calcite cements have δ18O values similar to those of their host carbonates, despite the fact that these calcites formed at elevated temperatures (>∼100°C). Based on petrographic and geochemical analyses, the 18O-enriched calcites commonly occur with solid bitumens and have lower δ13C values compared with host rocks, suggesting thermochemical sulfate reduction (TSR) provided organic carbon for these calcite precipitation. During TSR, thermal oxidation of hydrocarbons generated the light carbon, and simultaneously the reduced sulfate ions provided the oxygen. Comparison of our study with the TSR calcites worldwide, a model for oxygen isotope behavior during TSR was established. Oxygen isotope compositions of TSR-related calcites are a function of isotope compositions and amounts of the initial anhydrite and pore waters. TSR shows two opposing effects on the δ18O values of calcites, depending on the δ18O ratios of the initial anhydrite. The reduction of anhydrite with relatively low δ18O values causes the calcite δ18O lower than theoretical values of calcites directly precipitated from pore waters. The heavy δ18O ratios of calcites formed during TSR are not only attributed to the 18O-enriched pore water resulting from extensive water-rock interaction, but also probably due to the involvement of anhydrite with high δ18O values.
Construction of the Hainan Free Trade Port from the perspective of regional cultural development
Authors: Xiu Chunliang , Li Tong
Published: January 2023

This study summarizes the internal relationship and mechanism of industrialization, business culture, and higher education that affect the development of modern industrial and commercial culture, and consequently, the construction of free trade ports in Hainan. The cases of Hong Kong, Singapore, and Dubai free trade ports were considered as references. Based on immigration, naturalization, and education in Hainan’s history, Hainan’s cultural base map, which influences the construction of modern industrial and commercial culture, was proposed to be formed by splicing and overlapping of the free, guarding, farming-reading, farming-marine, and immigrant cultures. The development course of Hainan in the past 30 years indicated that although Hainan has always been at the forefront and highland of reform and opening up, it is still relatively backward despite the implementation of long-term policies; moreover, its development performance is not ideal. The existing problems and factors related to the present ideology mainly include the following: 1) The pursuit of “making quick money” has led to the ups and downs of Hainan’s development. 2) Lack of innovation hinders functional improvement leading to poor sustainability. 3) The course of modern industrial civilization based on a cultural base map is short. 4) Although bottom-up industrialization plays a key role in the formation of modern industrial civilization, it is not followed by Hainan. Furthermore, the cultural development path of Hainan Free Trade Port construction should 1) strongly promote industrialization by overcoming the shortcomings of industrial development, 2) deepen the reform of the agricultural reclamation system, improve the business environment, and cultivate a healthy modern industrial and commercial culture, 3) standardize the tourism market, and build the most advanced tourism industry culture, 4) improve the basic education level and develop excellent higher education opportunities, 5) enhance the diversity of human resources structure, and 6) revitalize literature and art, and showcase and develop Hainan’s fine culture. Overall, the construction of the Hainan Free Trade Port requires long-term upgrading and development. It is necessary to continue cultural construction, adapt to the requirements of the highest level of openness and realize the healthy development of the Hainan Free Trade Port.
Landslide susceptibility mapping in the Loess Plateau of northwest China using three data-driven techniques-a case study from middle Yellow River catchment
Authors: Guo Zizheng , Tian Bixia , Li Guangming , Huang Da , Zeng Taorui , He Jun , Song Danqing
Published: January 2023

Accurate landslide susceptibility maps are relevant for stakeholders to take effective measures and perform land use planning. The present research aims at using three data-driven approaches to generate landslide susceptibility map for the middle Yellow River catchment (northwest China) and comparing their performances, including the weighted information value (WIV), where the IV model was integrated with analytic hierarchy process (AHP), the support vector machine (SVM) and the random forest (RF) models. A landslide inventory map including 684 historical landslides was generated first by visual interpretation of remote sensing images combined with a field survey. A total of 14 thematic layers were applied to serve as the landslides influencing factors. The Pearson correlation coefficient analyzed the correlation among these factors, and the C5.0 decision tree algorithm determined the factor importance. The results demonstrated the correlation between every two factors were all less than 0.5. Three factors (including distance to road, distance to river, and slope) were the most important contributions to the landslide occurrences in the region, whereas five factors (including NDWI, plan curvature, profile curvature, surface roughness, and aspect) had minor importance. All the models predict that most of the historical landslides are identified in moderate and high susceptibility areas. For the prediction percentage of landslides in high susceptibility areas, both SVM and RF models exceed 70%. The RF model represented the best performance, with high susceptibility zones accounting for 21.9% and landslide numbers accounting for 90.5%. The comparison among the receiver operating characteristic curves indicated that the accuracy was higher in the RF model than in the other two models: the area under the curve (AUC) for the RF was 0.904, whereas that for the WIV and the SVM were 0.845 and 0.847, respectively. Hence, the RF was proven suitable for assessing the landslide susceptibility in the region. Current results can provide valuable references for future studies and landslide risk mitigation strategies.
Multi-scale pore structure characteristics and main controlling factors analysis of Longtan formation shale in Northwest Guizhou
Authors: Huang Yuqi , Zhang Jinchuan , Zhang Peng , Tang Xuan , Yang Junwei
Published: January 2023

Marine-continental transitional shale strata are widely distributed in China and have high gas potential. The Longtan shales are a typical marine-continental transitional coal-bearing shale system in Northwest Guizhou. Low-temperature N2 adsorption experiments and high-pressure mercury injection experiments were carried out on the unweathered shale samples from Well JS-1. The multi-scale fractal dimensions were calculated based on the MESP (Menger-sponge) model, MESA (mercury saturation) model, and FHH (Frenkel-Halsey-Hill) model respectively. The macropores (≥100 nm) are mainly inorganic with a fractal dimension D1 between 2.8628–3.2057, indicating the macropore structure is relatively complex. The proportion of the macropores in total pores is not high in comparison to mini-micropores (<50 nm), and the content of brittle minerals and pyrite mainly controls its structure. Among the mesopores (50–100 nm), inorganic pores are still the primary pore type, but the proportion of organic pores increases. The fractal dimension D2 is between 2.2125–2.3016. It has medium complexity, and the proportion in the total pores is slightly higher than that of macropores. The influence of organic matter abundance on mesopore structure is greater than that in macropore because of the increase in the proportion of organic pores, making the controlling mechanism of mesopore structure more complicated. Mini-micro pores are mainly organic pores. The fractal dimension D3 (fractal dimension of mini-micropores under low relative pressure, P/P0 ≤0.5) ranges between 2.6709–2.8648, and D3’ (fractal dimension of mini-micropores under high relative pressure, P/P0 >0.5) ranges between 2.6661–2.9256, indicating complex pore structures and rough surfaces. Mini-micropore accounts for the highest proportion of the total pores and its structure is mainly controlled by the abundance of organic matter. The pore structures of macropores and mesopores greatly influence the proportion of desorption gas in shale, while the structure of mini-micropores can control the maximum adsorbed gas volume of shale.
Spatio-temporal assessment of regional scale evolution and distribution of glacial lakes in Himalaya
Authors: Mohanty Litan , Maiti Sabyasachi , Dixit Ankur
Published: January 2023

Glacial lakes are a potential threat to the livelihoods and precious infrastructures in the Himalayan region. The expansion of these lakes under the influence of global warming further poses a grievous risk of natural disasters in the form of glacial lake outburst flood (GLOF) that necessitates regular monitoring to reduce and mitigate its implications. This research focuses on the regional scale distribution and evolution of glacial lakes in the Himalayan mountain range with their causes. We used Landsat thematic mapper (TM) and operational land imager (OLI) images, Google Earth imageries, Shuttle radar topographic mission (SRTM) Digital Elevation Model, and Aphrodite climatic data to study lake evolution and its controlling parameters. A total of the 5,409 glacial lakes was taken for the size expansion analysis, which excludes supraglacial lakes. An expansion rate of 2.98%/yr and 1.01%/yr in glacial lakes number and size was found from 1990 to 2020, respectively. The glacial lakes are distributed mainly in Langtang, Bhutan, Sikkim and Everest region; while, new lakes are forming at higher elevations continuously. The highest lake size expansion was noted in 2015–2020 (36.51%) followed by 2000–2010 (21.72%) and 2010–2015 (10.65%), while 1990–2000 (3.36%) showed a lowest expansion rate. The highest expansion rate was noticed near an elevation band of 5000–5500 m. Moreover, lakes in the central and eastern Himalaya are highly decrease by climatic change, i.e., increase in temperature a decrease precipitation. The feature selection algorithm was used to identify the importance of various controlling parameters, which showed temperature change rate, glacier fed lake, glacier snout steepness, proximal distance, glacier calving frontal width, precipitation change rate and lake type gave higher weightage towards lake size change.
Effects of diagenesis on quality of dengying formation deep dolomite reservoir, Central Sichuan Basin, China: Insights from petrology, geochemistry and in situ U-Pb dating
Authors: Gu Yifan , Wang Zhanlei , Yang Changcheng , Luo Mingsheng , Jiang Yuqiang , Luo Xiaorong , Zhou Lu , Wang Haijun
Published: January 2023

The Ediacaran Dengying Formation in Central Sichuan Basin is the deep dolomite gas reservoir with the largest natural gas reserves in China, providing an excellent example for understanding the effect of diagenesis evolution on deep dolomite reservoir quality. By integrating petrology, geochemistry and in situ U-Pb dating, this study aims to reveal the genesis of different rock fabrics and their corresponding diagenetic events, and to discuss the temporal relationship of diagenetic events and their effects on the reservoir quality of Dengying Formation. Two phases of dolomite and three phases of dolomite cement are identified in Ediacaran Dengying Formation deep dolomite reservoirs of Central Sichuan Basin as follows: 1) matrix dolomites (MD), 2) fine-medium crystalline dolomites (FMD), 3) fibrous dolomites (FD), 4) medium-coarse crystalline dolomites (MCD), and 5) saddle dolomite (SD). By analyzing petrographic and temporal relationships between these fabrics, it is suggested that the deep dolomite reservoir of Dengying Formation in Central Sichuan Basin has experienced six diagenetic stages, including 1) syndiagenetic stage, 2) the first-time early diagenetic stage, 3) epidiagenetic stage, 4) the second-time early diagenetic stage, 5) middle diagenetic stage and 6) late diagenetic stage. Microbial dolomitization during syndiagenetic stage produced limited increase in reservoir porosity, but it is of great significance for preservation of reservoir spaces. Silicification is most unfavorable for reservoir formation, but its duration and influence range are very limited. At epidiagenetic stage, the physical properties of Dengying Formation dolomite reservoir have been greatly improved. Two-time early diagenetic stages are both destructive for preservation of reservoir spaces. During middle diagenetic stage, two-stage of hydrothermal alterations occurred, corresponding to Late Silurian to Devonian and Late Permian, respectively. Hydrothermal alteration of the MD is both constructive and destructive, but overall it is constructive, and the improvement of physical properties is limited. For the karstified MD, both two-stage hydrothermal alterations were destructive, resulting in damage of reservoir physical properties caused by cementation by two-stage SD and one-stage MVT minerals.
Numerical study on the rock breaking mechanism of high-pressure water jet-assisted TBM digging technique based on 2D-DEM modelling
Authors: Jiang Yalong , Zeng Jianjun , Jing Liujie , Xu Changjie , Xiong Fuyang
Published: January 2023

In order to improve the digging efficiency of tunnel boring machine (TBM) in high-strength and highly abrasive formations, high-pressure water jet-assisted tunnel boring machine rock breaking technology has been developed and applied in steps. In this study, rock breaking mechanism by the new technology is investigated based on two-dimensional particle flow code (PFC2D) modelling. The force chain field distribution law and crack extension evolution characteristics of three typical rock breaking models are studied, and the influence of precutting slits parameters on force chain field distribution, rock sample rupture pattern, and peak load are further analysed. The results show that: 1) The rock breaking processes of the three typical modelling types (i.e., complete cutting model, same trajectory cutting model, and different trajectory cutting model) are different. Among them, the different trajectory cutting model is more likely to produce tensile failure and effectively reduce the penetration depth required for rock breaking. 2) The percentages of tension cracks to the total cracks in the three typical modellings are 90.8%, 93.9%, and 89.8%, respectively, indicating that the above three models are dominated by tension damage in the mesoscopic view. 3) With the increase of the depth of the precutting slit, the depth of the stress concentration zone beneath the disc cutter increases, inducing the increase of the angle between the edge of the stress concentration zone and the upper surface of the rock sample. Meanwhile, the peak load decreases, hence the difficulty of the tunnel boring machine disc cutter penetration is gradually reduced.
Comparative study of elastic properties of marl and limestone layers in the Eagle Ford formation
Authors: Jiang Shuxian , Mokhtari Mehdi , Song Jinze
Published: January 2023

Eagle Ford Formation has significant heterogeneity due to the existence of marl and interbedded limestone layers. The objective of this paper is to study the elastic properties of different layers in the Eagle Ford Formation. To achieve the goal, the relationships between compressional and shear velocities in marl and limestone layers were investigated in two representative Eagle Ford wells. These empirical equations can be used to estimate the shear velocity in Eagle Ford wells without sufficient well log data. Moreover, correlations between elastic properties and GR were obtained. Among all layers in the Eagle Ford Formation, marl layers of the lower Eagle Ford have the lowest averaged values of compressional velocity, shear velocity and dynamic Young’s modulus, while the limestone layers of the upper Eagle Ford have the highest averaged values of these three elastic parameters. In addition, the effect of elastic properties of shale layers on the aspect ratio of unconfined and confined fractures were evaluated. The influence of Young’s modulus contrast of shale layers on the aspect ratio of confined fractures was remarkable.
Impacts of train-induced dynamic loads on goaf foundation of Qinshui coalfield
Authors: Wang Hui , Zhou Jing , Cheng Jianhua , Dun Zhilin , Dun Zhiyuan
Published: January 2023

For the high-speed railway built in the goaf sites, if the influence depth of the additional loads reaches the collapse fault zone of the goaf foundation, the overburden rock mass above the mined area will move again, causing the surface to deform again, which seriously threatens the construction, operation, and maintenance of the high-speed railway lines. Therefore, in order to improve the safety and stability of operation of high-speed railway in goaf sites, it is essential to determine the activation deformation of the goaf foundation. In this paper, based on the additional stress method, the newly added embankment materials are taken as uniformly distributed strip static loads, and the high-speed railway in operation is regarded as the fluctuation-concentrated dynamic loads. The 1/4 vehicle vibration model with two degrees of freedom is introduced, and the influence depth of the additional loads of the goaf foundation is calculated. The criterion of activation is proposed based on the relationship between the influence depth of additional loads and the height of the collapse zone and fault zone. Conclusions drawn are as follows: i) the activation judgment criterion for the goaf foundation under the influence of high-speed railway vibration loads is recommended; ii) case study shows that the rail surface vibration model applicable to quantify the influence depth of high-speed railway mentioned previously mined-out regions; iii) the influence of rail surface irregularity on influence depth cannot be ignored; iv) the research conclusion can provide reference for site selection of high-speed railway and embankment deformation analysis.
Study on crack propagation in layered rock under the three-point bending conditions
Authors: Yang Yingming , Ma Zhibo , Zhang Weilong , Liu Gang , Zhang Peng
Published: January 2023

The pattern of layered rock crack propagation in mining and geotechnical engineering directly influences the production efficient of coal mines and the safety of workers. To reveal the characteristics of crack propagation in layered rock, the three-point bending experiment and numerical investigation were carried out to study the crack propagation process of single sandstone samples, sandstone-sandstone-sandstone combined samples, and sandstone-mudstone-sandstone combined samples. Using digital speckle correlation methods and acoustic emission techniques, the crack propagation process of the specimens was examined. The results show that the main factors affecting crack propagation include rock layer strength, bedding plane strength, and the position of pre-existing fractures. The presence of the bedding plane hinders the propagation of cracks, and when the bedding plane’s strength decreases, cracks that originated from the bedding plane spread horizontally along it. The weakening of the intermediate rock layer strength of the combined samples can lead to the initiation of microcracks within it earlier than macroscopic cracks, allowing many options for the initiation and propagation of following cracks. Meanwhile, the load-time curves of the combined samples during the experiment displays a double-peak characteristic. Furthermore, the presence of pre-existing fractures inside the layered rock might result in the unpredictability of the crack starting point and subsequently influence the crack propagation course.
Fluorine in shallow groundwater in China: A review of distribution, occurrence and environmental effects
Authors: Zhao Ping , Zhang Shuheng , Xu Kaijian , Zhao Yuejiao , Shen Pengju , Zhu Lele , Zheng Liugen
Published: January 2023

With rapid economic development and the increasing demand for drinking water, a large amount of groundwater is exploited, resulting in a high F− content in groundwater, which is harmful to the environment and human body. In this study, 5,464 data points of fluoride in shallow groundwater were collected, and the F− content distribution, occurrence form and environmental impact of shallow groundwater were discussed. The results showed that 1) the F− content in shallow groundwater in China ranged from 0 to 60 mg/L, with a mean content of 0.90 mg/L; the lowest average F− content in shallow groundwater in Southwest China was 0.36 mg/L; South China (1.20 mg/L), Northeast China (1.25 mg/L) and Northwest China (1.25 mg/L) were considered high-fluoride areas, and North China (0.93 mg/L), East China (0.67 mg/L) and Central China (0.80 mg/L) were considered low-fluoride areas. The mean F− content in groundwater differed between provinces and cities. 2) The F− in shallow groundwater mainly occurred in ionic, complex ionic and organic fluoride molecular states. 3) The influence of a high F− content in shallow groundwater on the environment was mainly manifested in the increase in water F− concentration and soil F− and vegetable F− content. The influence of a high F− content on the human body was mainly manifested in an increase in urinary F− content in children, a high prevalence of dental fluorosis in children, an increase in skeletal fluorosis rate in adults with age, and an influence on cognitive function of older adults. These results provide a basis for F− pollution control and high-fluoride water treatment.
Sensitivity of boundary layer parameterization schemes in a marine boundary layer jet and associated precipitation during a coastal warm-sector heavy rainfall event
Authors: Shen Yian , Du Yu
Published: January 2023

The sensitivity of planetary boundary layer (PBL) parameterization schemes in a marine boundary layer jet and associated precipitation is investigated in this study. Six PBL parameterization schemes in the Weather Research and Forecasting Model, including YSU, MYJ, MYNN, ACM2, BouLac, and UW schemes, are examined in simulating a marine boundary layer jet (BLJ) over South China Sea and associated coastal precipitation during a warm-sector heavy rainfall event (19–20 May 2015) near the coast of South China. The results show that YSU, MYJ, MYNN, and BouLac schemes can generally reproduce the coastal warm-sector heavy rainfall with 6-h accumulated precipitation exceeding 50 mm, but not for the ACMs and UW schemes. No convection initiation occurs in the ACM2 run, while rainfall is located to further north with weaker intensity in the UW run. Meanwhile, weakest and strongest BLJs are simulated in the ACM2 and UW runs, respectively. In the ACM2 run, the weaker BLJ with the maximum wind speed less than 17 m s−1 induces weaker convergence and lifting in the upwind side of the coastal terrain as well as less water vapor transport to the coastal area, which thus inhibit convection initiation. On the contrary, the too strong BLJ in the UW run with large area of wind speed greater than 18 m s−1 causes the northward movement of convection along with cold pools, and rainfall moves further north accordingly. The differences in BLJs’ strength among PBL schemes are attributed to varying simulated low-level vortex on the northern side of the BLJ through veering ageostrophic winds. The intensity of the simulated low-level vortex is affected by variations in boundary layer mixing over land and associated vertical temperature stratification under different PBL schemes.
Water level fluctuation controls carbon emission fluxes in a shallow lake in China
Authors: Yuan Xiaomin , Liu Qiang , Li Shuzhen , Cui Baoshan , Yang Wei , Sun Tao , Wang Xuan , Li Chunhui , Cai Yanpeng , Li Miao , Zhou Jialiang
Published: January 2023

High-strength alterations in the water level due to extreme climate change and increased anthropogenic activities have implications for methane (CH4) and carbon dioxide (CO2) emission variations in shallow lakes. However, the consistency of the carbon emission flux in response to water-level fluctuations and temperature is still unclear. Here, we evaluated the water depth (WD) on the magnitude and variation sensitivity of CH4, CO2, and GHG, and then the temperature dependence of carbon emissions was estimated at different water levels. The water depth threshold indicated a maximum CH4 (97.5 cm) and CO2 (10 cm), resulting in a water depth threshold of GHG at 54.6 cm. Inside the whole WD, the effect of rising water depth on CH4, CO2 and GHG sensitivity shifted from a positive effect to a negative effect at a WD of 97.5 cm. And CH4, CO2 and GHG in 10 cm<WD<97.5 cm show the highest emission flux and sensitivity to varying water depths. Furthermore, a consistency of carbon emission flux responding to water depth and temperature was only found in specific zones of shallow lakes with 10 cm<WD<97.5 cm, indicating that the temperature dependence of CH4 and CO2 are driven by the hydrological regime without water level stress, shifting the GHG emission flux. Ensuring the restoration management goal related to the carbon peak by governing the time of threshold occurrence is essential.
Effect of pre-confining pressure on unloading-induced coalburst: Insights from distinct element modelling
Authors: Cao Jinrong , Dou Linming , Zhou Kunyou , Kan Jiliang , Li Jiazhuo , Chai Yanjiang
Published: January 2023

Coalburst is a violent dynamic failure of coal during underground mining. It is of significance to study failure pattern as well as energy evolution and transition during coalbursts and how they are influenced by pre-confinement. This paper presents unloading-induced coalburst simulations using the distinct element method via a combined static–dynamic loading–unloading strategy. The numerical model is calibrated and validated by comparison with the failure process observed in laboratory tests. The influence of pre-confining pressure on unloading-induced coalburst was numerically investigated from the perspective of crack propagation, fracturing process, failure pattern, and energy evolution. In addition, failure mechanism and energy conversion during coalbursts under different pre-confining pressures are discussed. The results show that the stress change caused by sudden unloading of the pre-confining results in the initiation and development of cracks. Crack density and crack propagation velocity increase with increasing pre-confining pressure. As the pre-confining pressure increases, the coalburst becomes more intense and takes less time to be completed, and the main failure pattern in coalburst transforms from a tensile type to a shear type. In addition, the conversion ratio of kinetic energy and frictional energy during coalbursts increase non-linearly with increasing pre-confining pressure.
Molecular dynamics simulation and experimental study into effect of temperature on hardness of ice abrasives
Authors: Li Zhiping , Liu Yong , Wei Jianping , Wu Jiaojiao
Published: January 2023

Ice abrasive jet technology is a green and environmentally friendly process with wide application prospects in the field of surface treatment. Ice abrasive jets constitute an essential technical parameter of the process, and temperature affects the hardness of ice. Therefore, in this paper, we investigated the hardness of ice at different temperatures. The dynamic characteristics of ice at different temperatures were simulated using molecular dynamics methods, and the laws of the dynamic characteristics of ice with temperature were analysed. Hardness testing experiments were carried out to grade the hardness of ice and then linearly fitted the hardness versus temperature. The results show that as the temperature increased, the dynamic characteristics of ice changed correspondingly, and the intermolecular hydrogen bonds and van der Waals interactions of ice weakened. From a chemical perspective, with the increase in temperature the intermolecular force weakens, the lattice energy of the crystal decreases, the resistance required to destroy the crystal decreases, and the crystal exhibits low hardness. Temperature affects the hardness of ice by changing the strength of the intermolecular force. The experimentally measured ice hardness was classified into five classes, and the fit revealed a strong linear correlation between ice hardness and temperature. In this study, numerical simulations were performed and experimental results were analyzed to identify the effect of temperature on the hardness of ice by changing the force between ice molecules, which is crucial for improving the erosion efficiency of ice abrasive jets.
Numerical simulation of the effect of atmospheric condition on the lightning strike for wind turbine
Authors: Yang Ning , Jiang Wei , Jin Chenlu , Zhang Shuqin , Hou Wenhao
Published: January 2023

The risk of lightning exposure increases as wind turbine size increases, and lightning accidents have grown up to be a severe threat to wind turbines. The present paper focuses on the influence of the changes in atmospheric conditions around the rotating blade for the upward leader initiation. A 2D computational fluid dynamics model was established to obtain the air pressure distribution around the blades, and the simplified inception model was used to determine the initiation of the upward leader mechanism. In this paper, two significant factors of velocity and attack angle were studied. The results show that the trigger height is about an 11.2% difference for 120 m/s with the peak current of return stroke at 30 kA; the difference has reached about 28% for the attack angle of 10°. The research indicates that the area with higher air pressure is exposed to a greater risk of lightning strikes, and the probability of lightning strikes will increase as the blade attack angle increases.
K-feldspar pIRIR150 dating of the Late Pleistocene sediments in the NW Khangai Mountains (Mongolia) using a standardized dose-response curve approach
Authors: Li Yan , Tsukamoto Sumiko , Klinge Michael , Sauer Daniela , Frechen Manfred
Published: January 2023

K-feldspar luminescence dating has been widely applied to constrain the timing of Quaternary sedimentation in different environments. However, the measurements are time-consuming. Meanwhile, anomalous fading and partial bleaching are the two potential problems inducing dating uncertainty. In this study, sand-size K-feldspar grains extracted from 32 luminescence samples from the northern slope of the Khangai Mountains, Mongolia, were dated using the post-infrared (IR) infrared stimulated luminescence protocol (pIRIR150. subscript shows the second stimulation temperature). The standardized dose-response curves (sDRCs) for luminescence dating, which could improve the measurement efficiency, were constructed. The K-feldspar luminescence chronology has been established after careful investigations of fading correction and bleaching degree of the signals. The sDRCs and individual DRC yield consistent ages, indicating that sDRCs are applicable for luminescence dating with an improvement in measurement efficiency. The fading corrected ages using the two fading correction models are generally in agreement. Based on age comparisons between the radiocarbon dates, the fading corrected pIRIR150 and IR50 ages, the pIRIR150 signal was not fully bleached for several samples. In contrast, some IR50 ages were overestimated due to fading over-correction. The investigated profiles have documented the sedimentary information since the last deglaciation.