Discontinuous Areas Research Articles

Spatial variability of near-surface ground temperatures in a discontinuous permafrost area in Mongolia

Spatial variability of near-surface ground temperatures in a discontinuous permafrost area in Mongolia

Surface damage reduction effect of ultra-high working face in Shangwan coal mine

Green mining is the basic background of high-quality mining, and source reduction is the most important part, among which the optimization of working face height and length is the most active. How to control the working face parameters, reasonably evaluate the surface subsidence characteristics of the super-long working face, and identify the limit working face length and the surface discontinuous deformation threshold is particularly important. In order to solve the problem of irreversible damage to the surface caused by the mining process of the working face, this paper discusses the whole process of surface movement in the 8.8 m super-large mining height working face of Shangwan Coal Mine through field investigation, the maximum subsidence is 6.20 m, with a subsidence coefficient of 0.72. Combined with the inflection point trajectory, advancing degree and subsidence coefficient, the 0.9 coefficient of the working face subsidence basin boundary and the loss reduction strategy far from the limit working face threshold are proposed. The results show that the subsidence basin of 12,401 working face accounts for 34%, the continuous deformation area of surface accounts for 64%, and the influence area of discontinuous deformation area is within 10 times of mining height. With the help of borehole detection verification, the caving zone height within the coal seam overburden to be between 33.2 and 33.25 m and the fracture zone height between 118.08 and 132.83 m. Therefore, the caving ratio is about 3.8, and the fracture ratio is about 13–15, which provides a strong basis for the optimization design of working face and the timing of surface ecological management.

A new type of modified MR-WENO schemes with new troubled cell indicators for solving hyperbolic conservation laws in multi-dimensions

In this paper, a new type of increasingly high-order modified multi-resolution weighted essentially non-oscillatory (MMR-WENO) schemes with new troubled cell indicators is designed in the finite difference framework for solving hyperbolic conservation laws in one, two, and three dimensions. It is a first time to design new troubled cell indicators that based on two high-degree reconstruction polynomials, which are defined on the three-point, five-point, seven-point, and nine-point spatial stencils, respectively. Such new troubled cell indicators can automatically identify the discontinuous solutions without manually adjusting the parameters related to the problems. Subsequently, a series of MMR-WENO schemes are designed by using these new troubled cell indicators, which use the simple linear upwind schemes in smooth areas and the sophisticated MR-WENO schemes in discontinuous areas, thus achieving the goal of inheriting the excellent characteristics of original MR-WENO schemes while reducing computational costs. The new modified methodology is divided into two parts: if all extreme points of two reconstruction polynomials defined on the big spatial stencil are outward the smallest interval [xi−1/2,xi+1/2], the numerical flux is straightforwardly approximated by a high-degree reconstruction polynomial and the approximation has a high-order accuracy. Otherwise, the high-order MR-WENO spatial reconstruction procedures are adopted. The main benefits of new MMR-WENO schemes are their robustness and efficiency in comparison to original MR-WENO schemes, since the MMR-WENO schemes could save at most 63%-79% CPU time than the same-order MR-WENO schemes do for some numerical examples.

Seismic 3D full-horizon tracking based on a knowledge graph to represent the stratigraphic sequence relationship

Seismic 3D full-horizon tracking is a fundamental and crucial step in sequence analysis and reservoir modeling. Existing automatic full-horizon tracking approaches lack effective methods for representing the stratigraphic sequence relationships in seismic data. However, the inability to represent the stratigraphic sequence relationships fully and accurately makes it challenging to address discontinuous areas affected by faults and unconformities. To address this issue, we develop a knowledge graph representing the stratigraphic sequence relationship, which enables the simultaneous extraction of all horizon surfaces once the stratigraphic distribution of the seismic data is obtained. This method first generates horizon patches and calculates the fault attributes, followed by the construction of an initial knowledge graph that characterizes the overall distribution of horizon patches and faults. The initial knowledge graph comprises nodes and edges. The nodes represent horizon patches, and their attributes cover the geographical location information of the patches and faults. Simultaneously, the edges represent the relationship between the horizon patches, including the stratigraphic sequence relationship, and their attributes illustrate the potential for connecting these patches. Furthermore, we introduce a multilayer knowledge graph based on the point-set topology to fuse the nodes. This allows for the continuous merging of the horizon patches to obtain horizon surfaces across discontinuities with the constraints of fault attributes and stratigraphic sequence relationships in 3D space. Synthetic and field examples demonstrate that our approach can effectively represent stratigraphic sequence relationships and accurately track horizons located in discontinuous areas with faults and unconformities.

Effects of tillage microrelief units on splash erosion: A case study from the Loess Plateau, in China

A tillage microrelief unit is the smallest spatially discontinuous area unit of tillage microrelief. Understanding the impact of tillage microrelief units on splash erosion is essential for selecting suitable tillage measures and employing soil and water conservation practices. The objective of this study was to investigate the characteristics and mechanisms of splash erosion under different tillage microrelief units in various directions and distances using the rainfall simulation experiment in the soil landscape of the Loess Plateau region in China, characterized primarily by sloping farmland as the main land use type. Three typical microrelief units, namely, artificial digging (AD), contour tillage (CT), and straight slope conditions (SSC) were designed at 0°, 3°, 5°, 10°, 15°, and 20° slopes. Tillage microrelief units with high surface roughness produced more splash erosion than flat lands. Further, the highest surface roughness increased the total splash amount by 102% relative to flat lands. The tillage microrelief unit itself was elevated with a certain slope, which increased the downslope splash of CT, SSC, and AD by 121%, 173%, and 11%, respectively. Different surface roughness values and slopes under different microrelief units were used to determine the amount of splash erosion. The results showed that the total splash amount responded significantly (P < 0.01) to the interaction between surface roughness and slope, and the sensitivity to roughness was higher than that to slope. According to the single-factor analysis, the surface roughness of all slopes significantly influenced the amount of splash erosion. Furthermore, the sensitivity of the tillage microrelief unit to the slope decreased because of the high slope under high surface roughness. Overall, the results of this study showed that in different tillage microrelief units of slopes in the Loess Plateau, SSC and CT significantly increased the outward splash erosion in this area, while AD significantly decreased the outward splash erosion. Moreover, slope did not have a considerable influence.

Echotexture of recurrent laryngeal nerves: the depiction of recurrent laryngeal nerves at high-frequency ultrasound during radical thyroidectomy.

To investigate the ultrasound characteristics of recurrent laryngeal nerves (RLNs) during radical surgery for thyroid cancer and to enhance the understanding of RLN ultrasound features. From October 2021 to December 2022, a prospective study was conducted involving 24 patients scheduled for bilateral thyroid surgery. Near the conclusion of the surgery, intraoperative ultrasonography of the RLN within the tracheoesophageal groove was performed using a 15-7 MHz transducer. The thickness and width of the RLN were measured during the procedure. The internal architecture of the RLN was observed to consist of multiple hypoechoic, parallel, but discontinuous linear hyperechoic areas separated by bands. In the normal RLN group, the diameter of the RLN was relatively consistent, with thickness ranging from 2.20 to 2.71mm (mean: 2.48 ± 0.14mm) and width from 1.25 to 1.70mm (mean: 1.45 ± 0.11mm). Both weight and the body mass index (BMI) showed a statistically significant correlation with RLN thickness (Weight: r=0.544, P=0.001; BMI: r=0.605, P=0.001). The BMI also showed a statistically significant correlation with the RLN width (r=0.377, P=0.033). In the RLN invasion group, the width of invaded RLNs ranged from 1.9 to 2.3mm (mean: 2.10 ± 0.11mm), while the width of non-invaded RLNs ranged from 2.6 to 3.2mm (mean: 2.93 ± 0.20mm). Ultrasound effectively reveals the structural features of the RLN and enhances sonographers' understanding of RLN characteristics.

A novel coupled Euler–Lagrange method for high resolution shock and discontinuities capturing

AbstractThe accurate capturing of shock waves by numerical methods has long been a focus of attention in engineering owing to singularity problems in discontinuities. In this article, a novel coupled Euler–Lagrange method (CELM) is proposed to capture shock waves and discontinuities with high resolution and high order of mapping accuracy. CELM arranges the Lagrange particles on an Euler grid to track the discontinuous points automatically, and the data pertaining to the grids and particles interact via a weighted mutual mapping method that not only achieves fourth‐order accuracy in a smooth area of the solution but also maintains a steep discontinuous transition in the discontinuous area. In the virtual particle method, virtual particles are derived from the existing real particles; thus, the inflow and outflow of the particles and interpolation accuracy of the boundary are more easily realized. An accuracy test and energy convergence test demonstrated the fourth‐order convergence accuracy and low energy dissipation of the CELM; the method exhibited lower error and better conservation ability than high‐precision schemes such as WENO3 and WENO5. The Sod shock tube problem and Woodward–Colella problem showed higher discontinuity resolution of the CELM and ability to accurately track discontinuity points. Examples of Riemann problems were employed to prove that the CELM exhibits lower dissipation and higher shock resolution than WENO3 and WENO5. The CELM also showed an accurate structure based on particle distribution. Shockwave diffraction tests were conducted to prove that the CELM results showed good agreement with the experimental data and exhibited an accurate expansion wave. The CELM can also accurately simulate the collision of an expansion wave and vortex.

Tracking lake drainage events and drained lake basin vegetation dynamics across the Arctic

Widespread lake drainage can lead to large-scale drying in Arctic lake-rich areas, affecting hydrology, ecosystems and permafrost carbon dynamics. To date, the spatio-temporal distribution, driving factors, and post-drainage dynamics of lake drainage events across the Arctic remain unclear. Using satellite remote sensing and surface water products, we identify over 35,000 (~0.6% of all lakes) lake drainage events in the northern permafrost zone between 1984 and 2020, with approximately half being relatively understudied non-thermokarst lakes. Smaller, thermokarst, and discontinuous permafrost area lakes are more susceptible to drainage compared to their larger, non-thermokarst, and continuous permafrost area counterparts. Over time, discontinuous permafrost areas contribute more drained lakes annually than continuous permafrost areas. Following drainage, vegetation rapidly colonizes drained lake basins, with thermokarst drained lake basins showing significantly higher vegetation growth rates and greenness levels than their non-thermokarst counterparts. Under warming, drained lake basins are likely to become more prevalent and serve as greening hotspots, playing an important role in shaping Arctic ecosystems.

A study of a bio-inspired impact resistant carbon fiber laminate with a sinusoidal helicoidal structure in the mandibles of trap-jaw ants.

The majority of living organisms demonstrate remarkable attributes and have evolved effective mechanisms for synthesizing impact-resistant and damage-tolerant structures. One exemplary instance is the rapid mandible strikes exhibited by trap-jaw ants, which are a highly aggressive species of terrestrial social organisms. An impact-resistant sinusoidal helicoidal architecture is discovered in the mandibles of trap-jaw ants. The bioinspired laminate with a bi-sinusoidal helicoidal structure was manufactured using unidirectional carbon fiber prepreg by mold press forming. This study examines the impact resistance and damage tolerance of a bionic laminate through low velocity impact, computed tomography, and compression after impact tests. The results demonstrate that bionic laminates effectively limit damage propagation within the plane while enhancing energy dissipation capacity. The sinusoidal helicoidal configuration enhances cushioning capability against impact forces, retards penetration under higher loads, hinders crack propagation, and improves residual strength. Bionic laminates provide a valuable solution for damage tolerance through the resistance to through-the-thickness loads. STATEMENT OF SIGNIFICANCE: Helicoidal and sinusoidal helicoidal microstructures have been identified in the cross-section of the jaws of trap-jaw ants. The multiple waviness ratio parameters are designed for fabricating a sinusoidal helicoidal structure laminate using unidirectional carbon fiber prepreg through the mold press forming technique. This results in a damage-tolerant mechanism characterized by reduced delamination damage, which leads to a stiffer mechanical response. Meanwhile, it enhances resistance to crack propagation, leading to the formation of discontinuous delamination areas and the accumulation of sub-critical failures. Additionally, the sinusoidal helicoidal structure laminate combines the cushioning performance of bi-sinusoidal arrangements with the enhanced impact resistance of helical arrangements. This design delays penetration at higher loads, resulting in increased residual strength.

Hierarchical Edge-Preserving Dense Matching by Exploiting Reliably Matched Line Segments

Image dense matching plays a crucial role in the reconstruction of three-dimensional models of buildings. However, large variations in target heights and serious occlusion lead to obvious mismatches in areas with discontinuous depths, such as building edges. To solve this problem, the present study mines the geometric and semantic information of line segments to produce a constraint for the dense matching process. First, a disparity consistency-based line segment matching method is proposed. This method correctly matches line segments on building structures in discontinuous areas based on the assumption that, within the corresponding local areas formed by two corresponding line pairs, the disparity obtained by the coarse-level matching of the hierarchical dense matching is similar to that derived from the local homography estimated from the corresponding line pairs. Second, an adaptive guide parameter is designed to constrain the cost propagation between pixels in the neighborhood of line segments. This improves the rationality of cost aggregation paths in discontinuous areas, thereby enhancing the matching accuracy near building edges. Experimental results using satellite and aerial images show that the proposed method efficiently obtains reliable line segment matches at building edges with a matching precision exceeding 97%. Under the constraint of the matched line segments, the proposed dense matching method generates building edges that are visually clearer, and achieves higher accuracy around edges, than without the line segment constraint.

Numerical study of detonation propagation under the action of supersonic pulsating flow in expanding combustor

In this study, the effect of a velocity-pulsating stoichiometric hydrogen-oxygen mixture entering an expanding combustion chamber on the detonation wave is investigated. The hybrid sixth-order weighted essentially non-oscillatory centered difference scheme was used to solve the Navier–Stokes equations with a one-step two species chemistry model. The results verify that the induction zone is extended under the influence of pulsating flow. The discontinuous structure is formed in the flow field. A lot of unburned jets between the wavefront and the reaction zone were generated, which resulted in insufficient energy release. Coupled with the weakening of the wave strength by the Prandtl–Meyer (P-M) expansion fan, the detonation wave show different degrees of attenuation. The decay of the detonation wave shows different patterns at different amplitudes and periods. When the velocity amplitude is 0.3VCJ, the decay rate of detonation wave increases with the increase of the disturbance period. This attenuation law is different from the amplitude of 0.1VCJ and 0.2VCJ. This is because the discontinuous structure area formed by high-amplitude disturbance is large. Therefore, the longer its existence time is, the more serious the detonation wave attenuation is.

Permafrost Effect on the Spatial Distribution of CO2 Emission in the North of Western Siberia (Russia)

The landscapes in the discontinuous permafrost area of Western Siberia are unique objects for assessing the direct and indirect impact of permafrost on greenhouse gas fluxes. The aim of this study was to identify the influence of permafrost on the CO2 emission at the landscape and local levels. The CO2 emission from the soil surface with the removed vegetation cover was measured by the closed chamber method, with simultaneous measurements of topsoil temperature and moisture and thawing depth in forest, palsa, and bog ecosystems in August 2022. The CO2 emissions from the soils of the forest ecosystems averaged 485 mg CO2 m−2 h−1 and was 3–3.5 times higher than those from the peat soils of the palsa mound and adjacent bog (on average, 150 mg CO2 m−2 h−1). The high CO2 emission in the forest was due to the mild soil temperature regime, high root biomass, and good water–air permeability of soils in the absence of permafrost. A considerable warming of bog soils, and the redistribution of CO2 between the elevated palsa and the bog depression with water flows above the permafrost table, equalized the values of CO2 emissions from the palsa and bog soils. Soil moisture was a significant factor of the spatial variability in the CO2 emission at all levels. The temperature affected the CO2 emission only at the sites with a shallow thawing depth.

Numerical Simulation of Downward Flame Propagation in Discontinuous Region of Solid Fuel

This paper presents a numerical model that investigates the characteristics of flow, heat, and mass transfer on downward flame propagation in the discontinuous region of solid fuel. Simulations were carried out for various discontinuous distances to analyze the morphology of the flame front and the competition between the “jump” of flame spread and heat transfer from the flame to the unburned area. The results demonstrate that there is a “jump” in the flame propagation in the discontinuous zone, with the flame front exhibiting a defined “acute angle” that undergoes a process from large to small during the flame spreading in the discontinuous area and deflects towards the discontinuous area of the material. The temperature in the discontinuous zone reaches a peak, and the average flame spread rate initially increases and then decreases with the increase of discontinuity distance until the flame spread stops. The study provides valuable insights into the growth and development of fires involving discretely distributed combustible materials.

Enhancing the Urban Atlas Features with the Water Balance Estimates Using the Landsat 8 Imagery

Between climate change and anthropogenic forcing, pressure on water resources is continually increasing all over the world. The growing population is gathering more and more in cities where the artificialization of soils and urban developments of all kinds are modifying the local water cycle. However, knowledge about the hydrological cycle in urban areas is not well developed today. Urbanization in a watershed can produce significant changes to the natural water cycle, mainly because permeable soils have been covered by less permeable surfaces. The consequences of this urbanization can be significant and multiple. The assessment of urban water resources aims to provide a suitable circumstances for planning, conditions for the planning, design, construction, operation, and maintenance of works used for irrigation and sanitation, among other applications. The methodology of the research is based on the data collection, which includes climatic data from June 2021 to June 2022 and the use of Digital elevation model to create a hydrographic network. The second part is land use data processing to create a land cover map using maximum Likelihood Supervised Classification, by combining different band composites of Landsat 8 images and NDVI to differentiate between vegetative and non-vegetative areas. However, CORINE Land Cover database was utilized to distinguish between continuous and discontinuous urban area in this classification. The final step in the process is to determine the hydrological coefficients by calculating the water cycle parameters (Evapotranspiration Runoff and Infiltration) for each land-use class. Furthermore, establishing a link between land use and hydrological behaviour and conducting a precise calculation of water balance-related coefficients in urban areas using Urban Atlas 2018.

Effect of Moisture on CO&lt;sub&gt;2&lt;/sub&gt; Flux of the Palsa Mire Soils (North of Western Siberia)

The effect of the moisture content on peat soils has been studied in discontinuous permafrost area in the north of the Western Siberia (Nadym region). СО2 flux was measured in palsa mire soils (Cryic Histosol) and surrounding bogs (Fibric Histosol) using the closed chamber method for 4 years at the peak of the growing season (August). Despite a significant difference in soil moisture (34.8 ± 13.2 and 56.2 ± 2.1% on average), no significant difference in CO2 emission between these ecosystems was found in any of the observation years (on average 199.1 ± 90.1 and 182.1 ± 85.1 mg CO2 m–2 h–1, respectively). Experimental wetting or drying (with two times difference in moisture content) of peat soil plots by transplantation method showed no significant effect on CO2 emission even 3 years after the experiment start. The absence of significant differences in CO2 flux between ecosystems and experiments was explained by the presence of permafrost and the influence of many multidirectional factors mitigating changes in CO2 production by soils. CO2 flux enhancing from the soils of the bog is possible due to the additional contribution of the methanotrophic filter, as well as the lateral runoff of dissolved CO2 over the permafrost table from palsa mire surrounding the bogs. The absence of a response of CO2 emission to a significant change in moisture may indicate a wide optimum of this parameter for microbiological activity in peat soils of the studied region. The results indicate that, in the study of cryogenic soils of hydromorphic landscapes, it is necessary, in addition to biogenic sources, to take into account additional factors, often of a physical nature, that change the balance of CO2 fluxes and CO2 emission by soils, respectively.

Investigating the encrustation of reinforced ureteral stents by computational flow dynamic simulations

PurposeIn cases of extrinsic ureteral obstruction, obstruction due to encrustation is particularly detrimental to functioning of the stent. A thorough understanding of the causes that lead to stent encrustation is essential. Computational fluid dynamic (CFD) simulations may provide a reliable screening platform for investigating the interplay between flow processes and encrustation dynamics in stents.MethodsUsing a tailor-made program, we attempted to evaluate a number of reinforced ureteral stents by CFD simulations with an obstructed or unobstructed ureter and steady or discontinuous flow patterns to identify critical regions with abrupt changes in shape susceptible to stagnant flow and encrustation.ResultsFor the Vortek® and Urosoft stents, the longitudinal opening of the stents confirmed the presence of critical regions. No critical region was observed for the Superglide stent. CFD simulations showed that cavities formed near the critical regions represented patently stagnant flow and were potentially susceptible to the formation of encrusting deposits. Encrustations were greater in the obstructed design than in the unobstructed design. In the model with a suddenly interrupted laminar flow, the peristaltic motion resulted in new discontinuous encrustation areas scattered throughout the entire external and internal surface of the stent.ConclusionThe analysis of fluid dynamics through the tested stents confirmed that encrustations are possible in regions of stagnant flow and showed that stent models with the smoothest possible surface are preferable. The discontinuous flow model provided results that are closer to the findings observed in the clinic and should be more often integrated into CFD simulations.

Evidence of silicide at the Ni/[formula omitted]-Si3N4(0001)/Si(111) interface

We present a study of a sub-nanometre interlayer of crystalline silicon nitride at the Ni/Si interface. We performed transmission electron microscopy measurements complemented by energy dispersive X-ray analysis to investigate to what extent the nitride layer act as a barrier against atom diffusion. The results show that discontinuous silicide areas can form just below the nitride layer, whose composition is compatible with that of the nickel disilicide. The Ni–Si reaction is tentatively attributed to the thermal strain suffered by the interface during the deposition of Ni at low temperature.

Iteration of B-spline surface based deflectometric method for discontinuous specular surface

There is an over-growing demand for accurate three-dimension model of industrial components. In the measurement of specular surface, deflectometry has been widely used for its convenience and high accuracy. However, it is a challenge to measure discontinuous specular surface by the traditional deflectometry. In order to solve this problem, this paper proposes a deflectometric method based on iteration of control points of B-spline surface. In this method, a screen at two positions displays fringe patterns which will be reflected by specular surface under test and captured by a camera. According to the undistorted and absolute unwrapped phase map, a continuous zone containing all discontinuous area which is distinguished by a direct deflectometric method, is fitted by a B-spline surface with an estimated depth on the focus plane of the camera. Meanwhile, empty points and basis functions bridging isolated surface are removed. The control points of the fitted surface are solved by iterative calculation. With the solved control points, discontinuous specular surface is reconstructed. Simulated and actual experiments are carried out and the results show high accuracy and stability of the proposed method.

Modeling and experimental characterization of contact boundary tractions in non-conforming contact with random defects

An experimental characterization method for the non-conforming contact with random defects is developed in this paper. The method consists of the mechanics modeling and the parameters inversion algorithm. In the modeling, a new contact boundary description method is developed, which can sensitively characterize the discontinuous contact area caused by random defects. In the parameters inversion algorithm, an innovative objective function is designed by comprehensively considering the matching degree of displacements, the stability and singularity of boundary tractions. Combined with an iterative optimization method, the inversion algorithm can accurately identify random defects at different scales and characterize the evolution of contact boundary tractions. Numerical and experimental examples demonstrate that the method can provide reliable reconstruction results based on the displacement data.

Ore-containing data of lyalyagun mineralized zone of malguzar mountains

An analysis of the Malguzar Mountains allows us to note that Silurian formations (sandstones, gravestones, shale) are ore-bearing here, crumpled into folds, which are complicated by a series of faults with a northwest strike. These structures are rectilinear; their zone is characterized by the presence of small discontinuous structures and areas of swelling. Within the Lyalyagun zone, the localization sites of mineralized zones of gold mineralization were identified based on established direct and indirect cosmogeological features.