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Li, Zhao Kun, Hua Mei Bian, Li Juan Shi i Xiao Tie Niu. "Multiobjective Topology Extraction of the Compliant Mechanisms". Advanced Materials Research 971-973 (czerwiec 2014): 1941–48. http://dx.doi.org/10.4028/www.scientific.net/amr.971-973.1941.
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Homogenization or material distribution method based topology optimization will create final topologies in grey level image and saw tooth jump discontinuity boundaries that are not suitable for direct engineering practice, so it is necessary to extract the topological diagram. And a new topology extraction method for compliant mechanisms is presented. In the fist stage, the grey image is transferred into the black-and white finite element topology optimization results. The threshold value meeting to objective function is obtained so that each element is either empty or solid; in the second stage, the density contour approach is used by redistributing nodal densities to generate the smooth boundaries; in the third stage, Smooth boundaries are represented by parameterized B-spline curves whose control points selected from the viewpoint of stiffness and flexibility constitute the parameters ready to undergo shape optimization; Then shape optimization is executed to improve stress-based local performance, The parameters that present the outer shape of the compliant mechanism are used as design variables; In the final stage, simulations of numerical examples are presented to show the validity of the proposed method.
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EMOTO, Kazuma, Toshiyuki TSUCHIYA i Yoshinori TAKAO. "Numerical Investigation of Steady and Transient Ion Beam Extraction Mechanisms for Electrospray Thrusters". TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN 16, nr 2 (2018): 110–15. http://dx.doi.org/10.2322/tastj.16.110.
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Yang, Junyu, Qianghui Xu, Xuan Kou, Geng Wang, Timan Lei, Yi Wang, Xiaosen Li i Kai H. Luo. "Three-dimensional pore-scale study of methane hydrate dissociation mechanisms based on micro-CT images". Innovation Energy 1, nr 1 (2024): 100015. http://dx.doi.org/10.59717/j.xinn-energy.2024.100015.
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<p>Methane hydrate is a promising source of alternative energy. An in-depth understanding of the hydrate dissociation mechanism is crucial for the efficient extraction. In the present work, a comprehensive set of pore-scale numerical studies of hydrate dissociation mechanisms is presented. Pore-scale lattice Boltzmann (LB) models are proposed to simulate the multiphysics process during methane hydrate dissociation. The numerical simulations employ the actual hydrate sediment pore structure obtained by the micro-CT imaging. Experimental results of xenon hydrate dissociation are compared with the numerical simulations, indicating that the observed hydrate pore habits evolution is accurately captured by the proposed LB models. Furthermore, simulations of methane hydrate dissociation under different sediment water saturations, fluid flow rates and thermal conditions are conducted. Heat and mass transfer limitations both have significant effects on the methane hydrate dissociation rate. The bubble movement can further influence the dissociation process. Dissociation patterns can be divided into three categories, uniform, non-uniform and wormholing. The fluid flow impacts hydrate dissociation rates differently in three-dimensional real structures compared to two-dimensional idealized ones, influenced by variations in hydrate pore habits and flow properties. Finally, upscaling investigations are conducted to provide the permeability and kinetic models for the representative elementary volume (REV)-scale production forecast. Due to the difference in the hydrate pore habits and dissociation mechanisms, the three-dimensional upscaling results contrast with prior findings from two-dimensional studies. The present work provides a paradigm for pore-scale numerical simulation studies on the hydrate dissociation, which can offer theoretical guidance on efficient hydrate extraction.</p>
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Tomaszewska, Anna. "The Influence of Molar Extraction in Mandible on the Bone Remodeling Process under Different Chewing Conditions". Acta Mechanica et Automatica 19, nr 1 (1.03.2025): 148–52. https://doi.org/10.2478/ama-2025-0017.
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Abstract The aim of this study is to analyze the process of remodeling the mandibular bone in the context of functional adaptation after tooth extraction. The mandible, as a bone structure, undergoes continuous remodeling, allowing it to adapt to changing mechanical conditions. After tooth loss, significant changes occur in the distribution of loading, which can lead to bone resorption in areas with reduced mechanical stimulation and to excessive loading of the remaining teeth. The study utilizes a geometric model of the mandible, taking into account different chewing conditions before and after tooth extraction, as well as numerical simulations to assess changes in bone density. The results show significant changes in stress and bone density in the region of the extracted tooth, including an increase in the density of cortical and cancellous bone, confirming hypotheses regarding adaptive mechanisms. Understanding these processes is crucial for dental practice, enabling doctors to better plan therapy after tooth extractions and to avoid complications associated with tooth loss.
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Nguyen Dang Binh, Thanh, Dung Nguyen Trung i Duc Hong Ta. "MODELING OF ESSENTIAL OIL EXTRACTION PROCESS: APPLICATION FOR ORANGE, POMELO, AND LEMONGRASS". Vietnam Journal of Science and Technology 56, nr 4A (19.10.2018): 182. http://dx.doi.org/10.15625/2525-2518/56/4a/12811.
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ABSTRACT - HCTN - 44In this study, the kinetic models of steam distillation of orange (Citrus Sinensis (L.) Osbeck), pomelo (Citrus grandis L.), and lemongrass (Cymbopogon Citratus) for the recovery of essential oils were developed. The model parameters were estimated based on experimental data and comprehensive kinetic mechanisms of the solid-liquid extraction process. Numerical results showed that, the extraction mechanism of the three materials were best fit to the Patricelli two-stage model in which the diffusion of the oil was followed by the washing step. Moreover, the model parameters obtained from the measured data reflected clearly the nature of the two-stage extraction at which the kinetic rate of the washing step (surface extraction) was higher than that of in-tissue diffusion step. Thus, the kinetics of the extraction processes obtained from the present work could be used for the scale-up of the extraction process operating at a large scale and for the purpose of process control as well.
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Yang, Lei, Haonan Guo, Yu Dai i Wanheng Chen. "A Method for Complex Question-Answering over Knowledge Graph". Applied Sciences 13, nr 8 (18.04.2023): 5055. http://dx.doi.org/10.3390/app13085055.
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Knowledge Graph Question-Answering (KGQA) has gained popularity as an effective approach for information retrieval systems. However, answering complex questions involving multiple topic entities and multi-hop relations presents a significant challenge for model training. Moreover, existing KGQA models face difficulties in extracting constraint information from complex questions, leading to reduced accuracy. To overcome these challenges, we propose a three-part pipelined framework comprising question decomposition, constraint extraction, and question reasoning. Our approach employs a novel question decomposition model that uses dual encoders and attention mechanisms to enhance question representation. We define temporal, spatial, and numerical constraint types and propose a constraint extraction model to mitigate the impact of constraint interference on downstream question reasoning. The question reasoning model uses beam search to reduce computational effort and enhance exploration, facilitating the identification of the optimal path. Experimental results on the ComplexWebQuestions dataset demonstrate the efficacy of our proposed model, achieving an F1 score of 72.0% and highlighting the effectiveness of our approach in decomposing complex questions into simple subsets and improving the accuracy of question reasoning.
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Ban, Marko, i Neven Duic. "Adaptation of n-heptane autoignition tabulation for complex chemistry mechanisms". Thermal Science 15, nr 1 (2011): 135–44. http://dx.doi.org/10.2298/tsci100514077b.
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The adaptation of auto-ignition tabulation for effective use of complex chemical mechanisms will be presented in this paper. Taking cool flame ignition phenomenon into account could improve numerical simulations of combustion in compression ignition engines. Current approaches of successful simulation of this phenomenon are based on the extraction of ignition delay times, heat releases and also reaction rates from tabulated data dependant on four parameters: temperature, pressure, equivalence ratio and exhaust gasses mass fraction. The methods described here were used to create lookup tables including cool flame using a comprehensive chemical mechanism without including reaction rates data (as used by other authors). The method proved to be stable for creating tables and these results will be shown, as well as initial implementation results using the tables in computational fluid dynamics software.
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Ilic, Bojana, i Magdalena Djordjevic. "Understanding mass hierarchy in different energy loss mechanisms through heavy flavor data". EPJ Web of Conferences 276 (2023): 02017. http://dx.doi.org/10.1051/epjconf/202327602017.
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The theoretical analysis of experimental observations, such as the mass hierarchy effect, often neglects some ingredients, which may have a significant impact. The forthcoming measurements at RHIC and LHC will generate heavy flavor data with unprecedented precision, providing an opportunity to utilize high-p⊥ heavy flavor data to analyze the interaction mechanisms in QGP. To this end, we use our recently developed DREENA framework based on the dynamical energy loss formalism. We present: i) How to disentangle the signature of different interaction mechanisms (radiative and collisional energy losses) at the same dataset. ii) Novel observables susceptible to these different mechanisms to be tested by future high-precision measurements. iii) Analytical and numerical extraction of the mass hierarchy effect in energy losses through this observable.
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He, Siyuan, Fan Zhang, Weidong Hu, Lei Zhuang, Xingbin Ye i Guoqiang Zhu. "Investigation of Range Profiles from a Simplified Ship on Rough Sea Surface and Its Multipath Imaging Mechanisms". International Journal of Antennas and Propagation 2012 (2012): 1–6. http://dx.doi.org/10.1155/2012/894198.
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The range profiles of a two-dimension (2 D) perfect electric conductor (PEC) ship on a wind-driven rough sea surface are derived by performing an inverse discrete Fourier transform (IDFT) on the wide band backscattered field. The rough sea surface is assuming to be a PEC surface. The back scattered field is computed based on EM numerical simulation when the frequencies are sampled between 100 MHz and 700 MHz. Considering the strong coupling interactions between the ship and sea, the complicated multipath effect to the range profile characteristics is fully analyzed based on the multipath imaging mechanisms. The coupling mechanisms could be explained by means of ray theory prediction and numerical extraction of the coupling currents. The comparison of the range profile locations between ray theory prediction and surface current simulation is implemented and analyzed in this paper. Finally, the influence of different sea states on the radar target signatures has been examined and discussed.
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Qiao, Yu, Jie Zhang, Qiangqiang He, Yi Gu, Jun Wu, Lei Zhang i Chongjun Wang. "Truthful Profit Maximization Mechanisms for Mobile Crowdsourcing". Wireless Communications and Mobile Computing 2022 (22.01.2022): 1–13. http://dx.doi.org/10.1155/2022/8859905.
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Crowdsourcing is an effective tool to allocate tasks among workers to obtain a cumulative outcome. Algorithmic game theory is widely used as a powerful tool to ensure the service quality of a crowdsourcing campaign. By this paper, we consider a more general optimization objective for the budget-free crowdsourcer, profit maximization, where profit is defined as the difference between the benefit obtained by crowdsourcer and payments to workers. Based on the framework of random sampling and profit extraction, we proposed a strategy-proof profit-oriented mechanism for our problem, which also satisfies computational tractability and individual rationality and has a performance guarantee. We also extend the profit extract algorithm to the online case through a two-stage sampling. Also, we study the setting in which workers are not trusted, and untrustworthy workers would infer others’ true type. For untrustworthy workers, we introduce a differentially private mechanism, which also has desired properties. Finally, we will conduct numerical simulations to show the effectiveness of our proposed profit maximization mechanisms. By this work, we enrich the class of competitive auctions by considering a more general optimization objective and a more general demand valuation function.
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Yang, Chao, Guangsheng Luo, Xigang Yuan, Jie Chen, Yangcheng Lu, Xiaojin Tang i Aiwu Zeng. "Numerical simulation and experimental investigation of multiphase mass transfer process for industrial applications in China". Reviews in Chemical Engineering 36, nr 1 (18.12.2019): 187–214. http://dx.doi.org/10.1515/revce-2017-0050.
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Abstract This paper presents a comprehensive review of the remarkable achievements by Chinese scientists and engineers who have contributed to the multiscale process design, with emphasis on the transport mechanisms in stirred reactors, extractors, and rectification columns. After a brief review of the classical theory of transport phenomena, this paper summarizes the domestic developments regarding the relevant experiments and numerical techniques for the interphase mass transfer on the drop/bubble scale and the micromixing in the single-phase or multiphase stirred tanks in China. To improve the design and scale-up of liquid-liquid extraction columns, new measurement techniques with the combination of both particle image velocimetry and computational fluid dynamics have been developed and advanced modeling methods have been used to determine the axial mixing and mass transfer performance in extraction columns. Detailed investigations on the mass transfer process in distillation columns are also summarized. The numerical and experimental approaches modeling transport phenomena at the vicinity of the vapor-liquid interface, the point efficiency for trays/packings regarding the mixing behavior of fluids, and the computational mass transfer approach for the simulation of distillation columns are thoroughly analyzed. Recent industrial applications of mathematical models, numerical simulation, and experimental methods for the design and analysis of multiphase stirred reactors/crystallizers, extractors, and distillation columns are seen to garnish economic benefits. The current problems and future prospects are pinpointed at last.
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Ren, Zongxiao, Chenyu Zhang, Zhaoyang Fan i Yanfei Ren. "Numerical Simulation of Gas–Liquid–Solid Three-Phase Erosion in a Gas Storage Tank Tee". Lubricants 13, nr 1 (20.01.2025): 39. https://doi.org/10.3390/lubricants13010039.
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The objective is to address the issue of gas-carrying particles generated by erosion wear problems in the transportation process of gas storage reservoir pipelines. In accordance with the principles of the multiphase flow theory, the particle discrete phase model, high temperature, high pressure, water volume fraction, and other pertinent factors, this paper presents a three-phase gas–liquid–solid erosion mathematical model of a three-way gas storage reservoir. The effects of temperature, pressure, water content volume fraction, gas extraction, particle mass flow rate, and particle size on the tee’s erosion location and erosion rate were investigated based on this model. The findings indicate that, as the pressure and temperature decline, the maximum erosion rate of the tee exhibits a decreasing trend. Gas storage reservoir water production is relatively low, and its maximum erosion rate of the tee exerts a negligible influence. Conversely, the maximum erosion rate of the tee is significantly influenced by the gas extraction rate, exhibiting an exponential relationship with the maximum erosion rate and the rate of gas extraction. It was observed that, when the volume of gas extracted exceeded 70 × 104 m3/d, the maximum erosion rate of the tee exceeded the critical erosion rate of 0.076 mm/a. The maximum erosion rate of the tee caused by the sand mass flow rate remained relatively constant. However, the maximum erosion rate of the tee exhibited a linear correlation with the salt mass flow rate and the maximum erosion rate. The maximum erosion rate of the tee is greater than the critical erosion rate of 0.076 mm/a when the gas extraction volume is greater than 37.3 × 104 m3/d and the salt mass flow rate is greater than approximately 25 kg/d. As the sand and salt particle sizes increase, the maximum erosion rate of the tee initially rises, then declines, and finally stabilizes. The findings of this study offer valuable insights into the mechanisms governing tee erosion under elevated temperatures and pressures within storage reservoirs.
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Huang, Juehao, Yuwei Fang, Chao Wang, Zhihui Zhang i Yinan Li. "Research on 3D Geological and Numerical Unified Model of in Mining Slope Based on Multi-Source Data". Water 16, nr 17 (27.08.2024): 2421. http://dx.doi.org/10.3390/w16172421.
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As mining engineering progresses into the deep excavation phase, the intensification of high pressure, high temperature, strong disturbances, and complex geological conditions becomes increasingly prominent. Researchers perform stability analysis on the excavation area to reduce potential safety hazards during the extraction process. Developing a detailed numerical calculation model that accurately reflects the true geological structure is essential for numerical simulation analysis in mining engineering. Based on the excellent 3D geological modeling capabilities of 3D Mine software, this paper introduces a new 3D geological and numerical unified modeling method (3DMine-Rhino-HyperMesh) involving multi-software coupling and details the specific steps and concepts of this modeling approach. Subsequently, using a certain open-pit mine in Panzhihua as a backdrop, a detailed geological and numerical unified model is established, reflecting the true geological structure of the mining area, and the potential failure mechanisms of the mine slope are analyzed. The results indicate that the modeling method aligns well with the actual geological conditions, enhancing the grid quality of the numerical model and offering a new modeling approach for simulating and analyzing large complex geological entities in mining operations.
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Yoon, Hongkyu, Mart Oostrom, Thomas W. Wietsma, Charles J. Werth i Albert J. Valocchi. "Numerical and experimental investigation of DNAPL removal mechanisms in a layered porous medium by means of soil vapor extraction". Journal of Contaminant Hydrology 109, nr 1-4 (październik 2009): 1–13. http://dx.doi.org/10.1016/j.jconhyd.2009.07.001.
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Xing, Liru. "Study on Seepage of Coalbed Methane in Pore-fracture Double - porosity Medium". International Journal of Natural Resources and Environmental Studies 2, nr 1 (6.04.2024): 165–71. http://dx.doi.org/10.62051/10.62051/ijnres.v2n1.19.
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The study of coalbed methane (CBM) seepage within dual-porosity medium constitutes a significant research endeavor in the field of geology and coalbed methane reservoir engineering. This research delves into the complex dynamics governing CBM flow through porous coal matrices within dual-porosity systems. Employing advanced methodologies including numerical simulation and experimental analysis, this investigation aims to elucidate the mechanisms underlying CBM migration, encompassing diffusion and adsorption phenomena within the coal matrix, as well as interactions with adjacent strata. The outcomes of this study carry substantial implications for optimizing CBM extraction techniques and promoting the sustainable utilization of this invaluable natural resource.
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Liu, Zhiying, Qianghui Xu, Junyu Yang i Lin Shi. "Pore-Scale Modeling of Methane Hydrate Dissociation Using a Multiphase Micro-Continuum Framework". Energies 16, nr 22 (16.11.2023): 7599. http://dx.doi.org/10.3390/en16227599.
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The development of methane hydrate extraction technology remains constrained due to the limited physical understanding of hydrate dissociation dynamics. While recent breakthroughs in pore-scale visualization techniques offer intuitive insights into the dissociation process, obtaining a profound grasp of the underlying mechanisms necessitates more than mere experimental observations. In this research, we introduce a two-phase micro-continuum model that facilitates the numerical simulation of methane hydrate dissociation at both single- and multiscale levels. We employed this numerical model to simulate microfluidic experiments and determined the kinetic parameters of methane hydrate dissociation based on experimental data under various dissociation scenarios. The simulations, once calibrated, correspond closely to experimental results. By comprehensively comparing the simulated results with experimental data, the rate constant and the effective diffusion coefficient were reliably determined to be kd = 1.5 × 108 kmol2/(J·s·m2) and Dl = 0.8 × 10−7 m2/s, respectively. Notably, the multiscale model not only matches the precision of the single-scale model but also presents considerable promise for streamlining the simulation of hydrate dissociation across multiscale porous media. Moreover, we contrast hydrate dissociation under isothermal versus adiabatic conditions, wherein the dissociation rate is significantly reduced under adiabatic conditions due to the shifted thermodynamic condition. This comparison highlights the disparities between microfluidic experiments and real-world extraction environments.
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Alaghmand, S., S. Beecham i A. Hassanli. "Fully integrated physically-based numerical modelling of impacts of groundwater extraction on surface and irrigation-induced groundwater interactions: case study Lower River Murray, Australia". Natural Hazards and Earth System Sciences Discussions 1, nr 4 (26.07.2013): 3577–624. http://dx.doi.org/10.5194/nhessd-1-3577-2013.
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Abstract. Combination of reduction in the frequency, duration and magnitude of natural floods, rising saline water-table in floodplains and excessive evapotranspiration have led to an irrigation-induced groundwater mound forced the naturally saline groundwater onto the floodplain in the Lower River Murray. It is during the attenuation phase of floods that these large salt accumulations are likely to be mobilised and will discharge into the river. The Independent Audit Group for Salinity highlighted this as the most significant risk in the Murray–Darling Basin. South Australian government and catchment management authorities have developed salt interception schemes (SIS). This is to pump the highly saline groundwater from the floodplain aquifer to evaporation basins in order to reduce the hydraulic gradient that drives the regional saline groundwater towards the River Murray. This paper investigates the interactions between a river (River Murray in South Australia) and a saline semi-arid floodplain (Clarks Floodplain) significantly influenced by groundwater lowering (Bookpurnong SIS). Results confirm that groundwater extraction maintain a lower water-table and more fresh river water flux to the saline floodplain aquifer. In term of salinity, this may lead to less amount of solute stored in the floodplain aquifer. This occurs through two mechanisms; extracting some of the solute mass from the system and changing the floodplain groundwater regime from a losing to gaining one. Finally, it is shown that groundwater extraction is able to remove some amount of solute stored in the unsaturated zone and mitigate the floodplain salinity risk.
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Zhou, Peng, Chunyue Zhang, Jingkun Ai, Yongqiang Ge, Xiaoqing Peng, Qiaoling Gao, Wei Wang, Zhonghui Zhou i Jiawang Chen. "The Numerical Simulation and Experimental Study of Heat Flow in Seabed Sediments Based on COMSOL". Journal of Marine Science and Engineering 10, nr 10 (22.09.2022): 1356. http://dx.doi.org/10.3390/jmse10101356.
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In situ electrothermal conduction heating technology refers to the setting up of a heat source directly within the sediments, using the heat conductivity of the sediments and the heat radiation of the heat source for heat transfer to achieve the in situ heating of the sediments. The in situ electrothermal conduction heating of sediments has the disadvantage of the heating equipment being easily damaged and difficult to operate, and requires the equipment to be able to withstand seawater pressure and marine corrosion. In this paper, based on the combination of numerical simulations (using COMSOL Multiphysics software) and approximate in situ electrothermal conduction heating experiments, the temperature field and other factors of sediments heated by in situ conductive heating (in a specific area) were studied to determine a numerical model for sediment heat flow in a specific area under different pressures and initial temperatures, and the correctness of the numerical model was further verified by comparative experiments. The results of this study have important implications for future studies on the actual thermal properties of sediments and even heat transfer mechanisms during gas hydrate extraction.
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Lu, Yangbo, Feng Yang, Ting’an Bai, Bing Han, Yongchao Lu i Han Gao. "Shale Oil Occurrence Mechanisms: A Comprehensive Review of the Occurrence State, Occurrence Space, and Movability of Shale Oil". Energies 15, nr 24 (14.12.2022): 9485. http://dx.doi.org/10.3390/en15249485.
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Shale oil resources are important supplements for the gradually decreasing oil production from conventional reservoirs. Although the exploitation and development of shale oil have achieved considerable progress in the last decade, the commercial extraction of hydrocarbons from shales is still difficult, especially in the lacustrine sedimentary basins of China. One of the key points controlling the successful extraction of hydrocarbons from shale systems is the understanding of the occurrence mechanism of shale oil. This study comprehensively summarizes the theories and techniques to characterize oil occurrence state, occurrence space, oil content, and oil movability in shale systems. Sophisticated instruments, such as high-resolution scanning electron microscopy and high-energy ray imaging, were utilized to qualitatively analyze the pore networks of shales. Advanced physical experiments and numerical simulation techniques, including step-by-step rock pyrolysis, solvent extraction, and NMR, were introduced to characterize shale oil adsorption and movability. By the comparative analysis of the occurrence space, it is found that the image observation technique especially focuses on concentrated pores, such as organic matter-hosted pores. The fluid injection technology yields particular pore size information, which should be calibrated using other information. The 3D digital core, demonstrating the spatial distribution of minerals and pores, is an effective input for shale oil flow simulation. Geological controls analysis about oil retention in organic-rich shales has found that the inorganic matter pores and fractures are probably the “sweet spot” of shale oil, due to the low oil adsorption and high light hydrocarbons content. Many physical experiments measure the total free oil content but neglect the hydrocarbon–rock interaction and the sequential migration of hydrocarbon compounds. Thus, micro-scaled experiments measuring the hydrocarbon adhesion forces are needed to uncover the occurrence mechanism of shale oil in the future.
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Yeung, Albert T., i Subbaraju Datla. "Fundamental formulation of electrokinetic extraction of contaminants from soil". Canadian Geotechnical Journal 32, nr 4 (1.08.1995): 569–83. http://dx.doi.org/10.1139/t95-060.
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Electro-osmosis and ionic migration are the basic cleanup mechanisms in the electrokinetic extraction of contaminants from fine-grained soils. These are coupled flows as the flows of fluid and contaminants are driven by an externally applied electrical gradient. Moreover, other electrochemical reactions will occur simultaneously during the process. The most pronounced effect is the generation of pH gradient in the soil. The change of pH in the pore fluid can have a significant impact on the degree of sorption and desorption of chemicals on soil particle surfaces, complexes formation and precipitation of chemical species, and dissociation of organic acids; thus affecting the feasibility and efficiency of the cleanup technique tremendously. An attempt is made to formulate the coupled flows of ionic contaminants and the resulting change of pH in the pore fluid during the electrokinetic extraction process. The coupled flows of contaminants are formulated by the formalism of nonequilibrium thermodynamics. The pH is determined as a function of time and space by maintaining electrical neutrality throughout the system all the times. A numerical model NEUTRAL is developed to simulate the processes. The good agreement between computed and experimental results published in the literature indicates that the approach is a valid step toward a better understanding of the physics and chemistry involved during electrokinetic treatment of contaminated soils. Key words : electrokinetics, in situ remediation, contaminated soil, coupled flows, electrochemistry, nonequilibrium thermodynamics.
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Li, Biaomin, Shihong Xia, Wei Guo, Zhenhai Yang, Yuheng Zeng, Zhizhong Yuan i Jichun Ye. "Promoting Light Extraction Efficiency of Ultraviolet Light Emitting Diodes by Nanostructure Optimization". Crystals 12, nr 11 (10.11.2022): 1601. http://dx.doi.org/10.3390/cryst12111601.
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Ultraviolet (UV) light-emitting diodes (LEDs), as one of the more promising optoelectronic devices, are intrinsically limited by poor light extraction efficiencies (LEEs). To unlock the full potential of UV-LEDs, we propose a simple and effective strategy to promote the LEEs of UV-LEDs by screening and tailoring suitable optical structures/designs through rigorous numerical simulations. The photonic crystals (PCs) and/or nano-patterned sapphire substrates (NPSSs) equipped with the nano-pillar, nano-cone, nano-oval, and their derivates, are particularly investigated. The simulated results show that individual PC with an average transmittance of 28% is more efficient than that of individual NPSS (24.8%). By coupling PC and NPSS structures, a higher LEE with an average transmittance approaching 29% is obtained, much higher than that of the flat one (23.6%). The involved mechanisms are clarified and confirm that the promotion of optical performance of the nanostructured devices should be attributed to the widened response angles (from 0 to 60°), rather than the enhanced transmittances in the small angles within 30°.
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Zhao, Ziting, Chenglin Zhou, Jianfeng Zou, Jiaqi Sun i Yufeng Yao. "Detailed Numerical Simulation of Planar Liquid Sheet Atomization: Instability Dynamics, Ligament Formation, and Self-Destabilization Mechanisms". Fire 8, nr 5 (13.05.2025): 195. https://doi.org/10.3390/fire8050195.
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The primary atomization of planar liquid sheets near nozzle exits plays a critical role in the study of pressure-swirl atomizers, yet its intrinsic destabilization and breakup mechanisms remain insufficiently characterized due to the multi-scale nature of gas–liquid interactions, significantly limiting the predictive capacity of current widely adopted atomization models. This study utilizes three-dimensional direct numerical simulations (DNSs) with adaptive mesh refinement and the Volume-of-Fluid (VOF) method to examine the instability and disintegration of a spatially developing planar liquid sheet under operating conditions representative of aero-engine combustors (thickness h=100 μm, We=2544, Re=886). Adaptive grid resolution (minimum cell size 2.5 μm) enables precise resolution of multi-scale interface dynamics while maintaining mass conservation errors below 0.1‱. High-fidelity simulations reveal distinct atomization cascades originating from the jet tip, characterized by liquid sheet roll-up, interface expanding, interface tearing, and ligament/droplet formation. Through extraction and surface characterization of representative shed liquid ligaments, we quantify temporal and spatial variations between ligaments propagating toward and away from the jet core region. Key findings demonstrate that ligament impingement on the liquid core serves as the dominant mechanism for surface wave destabilization, surpassing the influence of initial gas–liquid shear at the nozzle exit. Spectral analysis of upstream surface waves reveals a pronounced correlation between high-wavenumber disturbances and the mean diameter of shed ligaments. These results challenge assumptions in classical atomization models (e.g., LISA) by highlighting self-destabilization mechanisms driven by droplet–ligament interactions. This work provides critical insights for refining engineering atomization models through physics-based ligament diameter prediction criteria.
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Whiting, Jonathan, Lysel Garavelli, Hayley Farr i Andrea Copping. "Effects of small marine energy deployments on oceanographic systems". International Marine Energy Journal 6, nr 2 (20.12.2023): 45–54. http://dx.doi.org/10.36688/imej.6.45-54.
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The placement and operation of marine energy deployments in the ocean have the potential to change flow patterns, decrease wave heights, and/or remove energy from the oceanographic system. Changes in oceanographic systems resulting from harvesting marine energy, particularly tidal and wave energy, may be of concern. These changes include alterations in nearfield and farfield physical processes, as well as potential secondary environmental effects such as changes in sediment transport patterns, biological processes, or coastal erosion. Knowledge of changes in oceanographic systems associated with marine energy is primarily available from numerical modeling studies, informed by some laboratory tests and very few field measurements. A literature review was conducted using the Tethys knowledge base and other online sources, building on conclusions from the Ocean Energy Systems-Environmental State of the Science report. Potential changes in oceanographic systems that may be caused by marine energy differ between tidal and wave devices because of different extraction mechanisms and siting locations. Numerical models show that tidal extraction on the order of hundreds of megawatts or with significant channel blockage is required to create changes in oceanographic processes that exceed natural variability. Effects from wave energy extraction in arrays are localized and dependent on array spacing and proximity to the shore. Available evidence supports the conclusion that the risk of significant environmental effects from such changes could be retired (i.e., less investigation required for every project) for small deployments—those representative of the state of the industry in 2021. Determining changes in oceanographic systems to be low risk for small deployments can thereby streamline environmental consenting by reducing monitoring needs at this early stage in the industry.
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Wang, Feng, Zeqi Jie, Bo Ma, Weihao Zhu i Tong Chen. "Influence of Upper Seam Extraction on Abutment Pressure Distribution during Lower Seam Extraction in Deep Mining". Advances in Civil Engineering 2021 (13.10.2021): 1–9. http://dx.doi.org/10.1155/2021/8331293.
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Pressure-relief coal mining provides an effective way to decrease stress concentration in deep mining and ensures mining safety. However, there is currently a lack of research and field verification on the pressure-relief efficiency and influencing factors during upper seam extraction on the lower seam. In order to make up for this deficiency, in this study, field measurements were conducted in panel Y485, which has a maximum depth of 1030 m and is partially under the goaf of the upper 5# seam in the Tangshan coal mine, China, and evolution of advanced abutment pressure was analyzed. Numerical simulations were conducted to study of influence of key strata on advanced abutment pressure. Influence mechanisms of the upper seam extraction on the advanced abutment pressure distribution during lower seam extraction were revealed. The results indicate that the distribution of advanced abutment stress is influenced by the key strata in the overlying strata. The key strata above the upper coal seam were fractured due to the upper coal seam mining, and the advanced abutment stress was only influenced by the key strata between the two seams during lower coal seam mining. When key strata were present between two seams, the extraction of the lower seam still faces potential dynamic disasters after the extraction of the upper seam. In this case, it would be necessary to fracture the key strata between the two seams in advance for the purpose of mining safety. Key strata in the overlying strata of the 5# seam were fractured during extraction, and advanced abutment pressure was only influenced by the key strata located between the two mined seams. The influence distance of advanced abutment pressure in panel Y485 decreased from 73 m to 38 m, and the distance between the peak advanced abutment pressure and the panel decreased from 29 m to 20.5 m, achieving a pronounced pressure-relief effect.
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Zhao, Zihan, Shaomu Wen, Mengyu Wang, Lianjin Zhang, Cheng Cao, Changcheng Yang i Longxin Li. "Experimental and Numerical Simulation Study on Enhancing Gas Recovery with Impure CO2 in Gas Reservoirs". Processes 12, nr 8 (8.08.2024): 1663. http://dx.doi.org/10.3390/pr12081663.
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To achieve carbon peaking and carbon neutrality goals, using CO2 to enhance natural gas recovery has broad application prospects. However, the potential for CO2 to increase recovery rates remains unclear, the mechanisms are not fully understood, and the cost of purifying CO2 is high. Therefore, studying the effects of impure CO2 on natural gas extraction is of significant importance. This study investigated the effects of injection timing and gas composition on natural gas recovery through high-temperature, high-pressure, long-core displacement experiments. Based on the experimental results, numerical simulations of CO2-enhanced gas recovery and sequestration were conducted, examining the impact of impurity gas concentration, injection timing, injection speed, and water saturation on recovery efficiency. The results indicate that higher impurity levels in CO2 increase gas diffusion, reducing the effectiveness of natural gas recovery and decreasing CO2 sequestration. Earlier injection timing improves recovery efficiency but results in a lower ultimate recovery rate. Higher injection speeds and water saturation levels both effectively enhance recovery rates.
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Strand, Roald, Greg Keir, Lucy Reading, Brent Usher i Chris Dickinson. "A rapid and flexible method for simulation of CSG water production: application in the Surat and Bowen basins". APPEA Journal 54, nr 1 (2014): 135. http://dx.doi.org/10.1071/aj13015.
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There is significant interest in estimating volumes of water extracted during production as the CSG industry develops in the Surat and Bowen basins in Queensland, Australia. Klohn Crippen Berger Ltd (KCB) was commissioned by the Queensland Department of Natural Resources and Mines (DNRM) to develop a tool to estimate where, when, and how much CSG water will be produced in these areas under various industry expansion scenarios. The tool, which is now being maintained and further developed to interface with GIS software by the Centre for Water in the Minerals Industry (CWiMI), was built to balance numerical complexity against relative flexibility and simulation speed. This was achieved by an approach that differs from conventional reservoir engineering models, including: the use of non-equilibrium groundwater flow equations (the Theis equation) in conjunction with semi-empirical type-curve based methods; calculation of well interference effects and corresponding spatial scaling effects in a relatively large-scale spatially discretised model; and, modification of flows predicted using the Theis equation to reflect the dual-phase nature of CSG extraction, and the unique hydrogeological setting of the eastern margin of the Surat Basin. The tool was verified against equivalent Theis equation calculations and type curves provided by CSG proponents. The tool was demonstrated to adequately represent the unique physical mechanisms of CSG extraction, and produce robust estimates of CSG water production at a regional scale, while not relying on excessively complex numerical models or excessive data input requirements.
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Chang, Shuai, Zhen Yang, Changfang Guo, Zhanyuan Ma i Xiang Wu. "Dynamic Monitoring of the Water Flowing Fractured Zone during the Mining Process under a River". Applied Sciences 9, nr 1 (23.12.2018): 43. http://dx.doi.org/10.3390/app9010043.
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The hydrogeological conditions of coal mines in China are quite complex, and water inrush accidents occur frequently with disastrous consequences during coal extraction. Among them, the risk of coal mining under a river is the highest due to the high water transmissivity and lateral charge capacity of the unconfined aquifer under the river. The danger of mining under a river requires the accurate determination of the developmental mechanisms of the water flowing fractured zone (WFFZ) and the water flow mechanisms influenced by the specific geological conditions of a coal mine. This paper first used the transient electromagnetic (TEM) method to monitor the development of the WFFZ and the water flow mechanisms following the mining of a longwall face under a river. The TEM survey results showed that the middle Jurassic coarse sandstone aquifer and the Klzh unconfined aquifer were the main aquifers of the 8101 longwall panel, and the WFFZ reached the aquifers during the mining process. Due to the limited water reserves in the dry season, the downward flowing water mainly came from the lateral recharge in the aquifer. The water inrush mechanisms of the 8101 longwall panel in Selian No.1 Coal mine were analyzed based on the water flow mechanisms of the aquifer and the numerical simulation results. This provides theoretical and technical guidance to enact safety measures for mining beneath aquifers.
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Gao, Amy, i Michael S. Triantafyllou. "Independent caudal fin actuation enables high energy extraction and control in two-dimensional fish-like group swimming". Journal of Fluid Mechanics 850 (4.07.2018): 304–35. http://dx.doi.org/10.1017/jfm.2018.456.
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We study through numerical simulation the optimal hydrodynamic interactions and basic vorticity control mechanisms for two fish-like bodies swimming in tandem. We show that for a fish swimming in the wake of an upstream fish, using independent pitch control of its caudal fin, in addition to optimized body motion, results in reduction of the energy needed for self-propulsion by more than 50 %, providing a quasi-propulsive efficiency of 90 %, up from 60 % without independent caudal fin control. Such high efficiency is found over a narrow parametric range and is possible only when the caudal fin is allowed to pitch independently from the motion of the main body. We identify the vorticity control mechanisms employed by the body and tail to achieve this remarkable performance through thrust augmentation and destructive interference with the upstream fish-generated vortices. A high sensitivity of the propulsive performance to small variations in caudal fin parameters is found, underlying the importance of accurate flow sensing and feedback control. We further demonstrate that using lateral line-like flow measurements to drive an unscented Kalman filter, the near-field vortices can be localized within 1 % of the body length, and be used with a phase-lock controller to drive the body and tail undulation of a self-propelled fish, moving within the wake of an upstream fish, to stably reach the optimal gait and fully achieve maximum energy extraction.
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Liu, Xianshan, Xiaolei Luo, Shaowei Liu, Pugang Zhang, Man Li i Yuhua Pan. "A Numerical Investigation of the Nonlinear Flow and Heat Transfer Mechanism in Rough Fractured Rock Accounting for Fluid Phase Transition Effects". Water 16, nr 2 (19.01.2024): 342. http://dx.doi.org/10.3390/w16020342.
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The study of the seepage and heat transfer law of three-dimensional rough fractures is of great significance in improving the heat extraction efficiency of underground thermal reservoirs. However, the phase transition effects of fluids during the thermal exploitation process profoundly influence the intrinsic mechanisms of fracture seepage and heat transfer. Based on the FLUENT 2020 software, single-phase and multiphase heat–flow coupling models were established, and the alterations stemming from the phase transition in seepage and heat transfer mechanisms were dissected. The results indicate that, without considering phase transition, the geometric morphology of the fractures controlled the distribution of local heat transfer coefficients, the magnitude of which was influenced by different boundary conditions. Moreover, based on the Forchheimer formula, it was found that the heat transfer process affects nonlinear seepage behavior significantly. After considering the phase transition, the fluid exhibited characteristics similar to shear-diluted fluids and, under the same pressure gradient, the increment of flow rate was higher than the increment in the linearly increasing scenario. In the heat transfer process, the gas volume percentage played a dominant role, causing the local heat transfer coefficient to decrease with the increase in gas content. Therefore, considering fluid phase transition can more accurately reveal seepage characteristics and the evolution law.
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Tong, Qing. "Theoretical Analysis of Foundation-Soil Interaction for Buildings in Mining Subsidence Areas". Scientific Journal of Technology 7, nr 3 (19.03.2025): 114–18. https://doi.org/10.54691/xy96b130.
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Mining-induced subsidence poses a significant challenge to the design and stability of buildings and infrastructure in areas where mineral extraction occurs. As the mining process causes shifts in the underground strata, the resulting surface settlement can have devastating effects on the foundations of buildings. The interaction between the foundation and the soil is crucial to understanding how these settlements affect structural integrity. This paper provides a comprehensive theoretical analysis of the foundation-soil interaction under mining-induced subsidence, focusing on the various mechanisms of settlement, soil behavior, and foundation response. Additionally, the paper explores modern techniques in foundation design, numerical modeling, and mitigation strategies to address the challenges presented by mining-induced settlements. Through this analysis, a robust framework for the safe design and maintenance of foundations in subsiding areas is proposed.
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Li, Weirong, Xin Wei, Zhengbo Wang, Weidong Liu, Bing Ding, Zhenzhen Dong, Xu Pan, Keze Lin i Hongliang Yi. "Numerical Investigation on Alkaline-Surfactant-Polymer Alternating CO2 Flooding". Processes 12, nr 5 (29.04.2024): 916. http://dx.doi.org/10.3390/pr12050916.
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For over four decades, carbon dioxide (CO2) has been instrumental in enhancing oil extraction through advanced recovery techniques. One such method, water alternating gas (WAG) injection, while effective, grapples with limitations like gas channeling and gravity segregation. To tackle the aforementioned issues, this paper proposes an upgrade coupling method named alkaline-surfactant-polymer alternating gas (ASPAG). ASP flooding and CO2 are injected alternately into the reservoir to enhance the recovery of the WAG process. The uniqueness of this method lies in the fact that polymers could help profile modification, CO2 would miscible mix with oil, and alkaline surfactant would reduce oil–water interfacial tension (IFT). To analyze the feasibility of ASPAG, a couples model considering both gas flooding and ASP flooding processes is established by using the CMG-STARS (Version 2021) to study the performance of ASPAG and compare the recovery among ASPAG, WAG, and ASP flooding. Our research delved into the ASPAG’s adaptability across reservoirs varying in average permeability, interlayer heterogeneity, formation rhythmicity, and fluid properties. Key findings include that ASPAG surpasses the conventional WAG in sweep and displacement efficiency, elevating oil recovery by 12–17%, and in comparison to ASP, ASPAG bolsters displacement efficiency, leading to a 9–11% increase in oil recovery. The primary flooding mechanism of ASPAG stems from the ASP slug’s ability to diminish the interfacial tension, enhancing the oil and water mobility ratio, which is particularly efficient in medium-high permeability layers. Through sensitivity analysis, ASPAG is best suited for mid-high-permeability reservoirs characterized by low crude oil viscosity and a composite reverse sedimentary rhythm. This study offers invaluable insights into the underlying mechanisms and critical parameters that influence the alkaline-surfactant-polymer alternating gas method’s success for enhanced oil recovery. Furthermore, it unveils an innovative strategy to boost oil recovery in medium-to-high-permeability reservoirs.
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Li, Guoyi, Rajesh Kumar Neerukatti i Aditi Chattopadhyay. "Ultrasonic guided wave propagation in composites including damage using high-fidelity local interaction simulation". Journal of Intelligent Material Systems and Structures 29, nr 5 (19.09.2017): 969–85. http://dx.doi.org/10.1177/1045389x17730659.
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Composite materials are used in many advanced engineering applications because of high specific strength and stiffness. Their complex damage mechanisms and failure modes, however, are still not well-understood, thus challenging the application safety. Ultrasonic guided waves are promising structural health monitoring tools used to determine the operational safety of composite materials. In this article, a fully coupled numerical simulation model is used to study wave propagation and dispersion in composites under varying sensor locations, propagating orientations, excitation frequencies, and damage locations. The model is based on the local interaction simulation approaches/sharp interface model wherein output sensor signals are processed using the matching pursuit decomposition algorithm to study the signal features in the time–frequency domain. The changes in signals due to varying damage locations with respect to the through-thickness direction are studied under anti-symmetrical and symmetrical excitation scenarios. The results show that the signal from symmetric excitation is more sensitive to the damage location, while the signal from anti-symmetric excitation is less dispersive. It indicates that comprising effective feature extraction technique with the accurate physics-based numerical simulation model can be implemented to develop robust structural health monitoring framework for composites.
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Zhu, Fang-Yin, Shui-Rong Chai, Li-Xin Guo, Zhen-Xiang He i Yu-Feng Zou. "Intelligent RCS Extrapolation Technology of Target Inspired by Physical Mechanism Based on Scattering Center Model". Remote Sensing 16, nr 13 (8.07.2024): 2506. http://dx.doi.org/10.3390/rs16132506.
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In this paper, a technology named SCM−ANN combining physical scattering mechanisms and artificial intelligence is proposed to realize radar cross-section (RCS) extrapolation of non-cooperative conductor targets with higher efficiency. Firstly, an adaptive scattering center (SC) extraction algorithm is used to construct the scattering center model (SCM) for non-cooperative targets from radar echoes in the low-frequency band (LFB). Secondly, an artificial neural network (ANN) is constructed to capture the nonlinear relationship between the real LFB echoes and those reconstructed from the SCM. Finally, the SCM is used to reconstruct echoes in the high-frequency band (HFB), and these reconstructions, together with the trained ANN, optimize the extrapolated HFB RCS. For the SCM−ANN technology, physical mechanistic modes are used for trend prediction, and artificial intelligence is used for regression optimization based on trend prediction. Simulation results show that the proposed method can achieve a 50% frequency extrapolation range, with an average prediction error reduction of up to 40% compared with the traditional scheme. By incorporating physical mechanisms, this proposed approach offers improved accuracy and an extended extrapolation range compared with the RCS extrapolation techniques relying solely on numerical prediction.
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Ostroverkh, Borys, i Lyudmila Potapenko. "NUMERICAL METHOD FOR ASSESSING EFFICIENCY OF WAVE ENERGY CONVERTOR INTEGRATED INTO COASTAL PROTECTION STRUCTURES". Bulletin of the National Technical University "KhPI". Series: Mathematical modeling in engineering and technologies, nr 1 (1.08.2023): 169–76. http://dx.doi.org/10.20998/2222-0631.2023.01.25.
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The use of wave energy by converting it into electricity depends on the efficiency of wave energy converters, which are negatively affected by marine factors. Many design flaws can be eliminated at the stage of design and testing of devices by using its numerical models based on the application of the hydrodynamic theory of propagation and interaction of waves with marine structures. The use of the modern computational methods of hydrodynamics to determine the influence of some design factors of wave energy converters incorporated into a submerged breakwater is considered in the paper. The results of numerical studies showed that if a submerged breakwater is located in the wave stream and with a transducer installed on its crest, there is a change in flow velocities and pressure in the transducer chamber, which affects the efficiency of energy extraction. Additional advantages arise as a result of the introduction of a complex structure with coastal protection and power supply functions. The obtained calculation results visualize the qualitative indicator of the influence of the design factors of the converter. Additional conclusions can be obtained by processing the numerical results. As a result of numerical experiments conducted with using REEF3D CFD computer system, the measures for selecting the parameters of the converters were proposed based on mathematical modeling of specific structures. The research related to the determination of the mechanisms of wave energy transformation when interacting with coastal protection elements focused on increasing the efficiency of the convertor by locating in deeper water, which includes detailed testing, investigations and improvement of various types of constructions, is carried out on the computing and laboratory base of Institute of Hydromechanics.
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Chang, Xiaoke, Jianxi Ren, Rong Yang i Yan Tong. "Study on tunnel ventilation and pollutant diffusion mechanism during construction period". PLOS One 20, nr 5 (12.05.2025): e0322984. https://doi.org/10.1371/journal.pone.0322984.
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Ventilation technology is an important means to ensure effective control of pollutant concentration and safe production during tunnel drilling and blasting construction. This study combines theoretical derivation, numerical simulation, and mathematical statistics to explore the extraction of flow field distribution characteristics and pollutant transport and diffusion mechanisms in tunnels. The research results indicate that the instability and turbulence effects of fluids work together to form a vortex zone near the tunnel working face. Fluid instability refers to the tendency of fluids to undergo changes under the influence of tunnel sidewalls or airflow in ducts. Turbulence effect is caused by the chaotic and irregular flow of fluids, leading to fluid mixing and rotation. The complex flow field changes inside the tunnel result in the retention of pollutants generated during construction in specific zone. The main reasons for the formation of pollutant stagnant zones are the bypass effect, low-velocity regions, and vortex of fluid. The emission process of pollutants can be divided into two stages: extraction and dilution. The dilution effect of pollutants is inversely proportional to the distance between the air duct and the working face, and the extraction amount is directly proportional to the airflow of the fan. The shorter distance allows fresh air to directly reach high concentration pollutant zone from the air duct, accelerating the mixing and dilution process. A larger airflow can provide stronger power and carry more pollutants out of the tunnel. The improved Technique for Order Preference by Similarity to an Ideal Solution method can optimize the layout of ventilation parameters and improve ventilation conditions. Finally, an empirical calculation formula for air supply volume is derived through in - depth research and data analysis. This formula takes into account multiple factors related to the tunnel structure, pollutant generation, and ventilation requirements. This empirical formula provides a scientific basis for the selection of ventilation fans in the construction preparation stage. Construction planners can accurately calculate the required air supply volume according to the specific situation of the tunnel, and then select the appropriate ventilation fan, which can not only ensure the ventilation effect but also save energy and reduce costs.
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Xin, Yicheng, Zheng Yuan, Yancai Gao, Tao Wang, Haibiao Wang, Min Yan, Shun Zhang i Xian Shi. "Numerical Simulation of Hydraulic Fracture Propagation in Unconsolidated Sandstone Reservoirs". Processes 12, nr 10 (12.10.2024): 2226. http://dx.doi.org/10.3390/pr12102226.
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In order to comprehensively understand the complex fracture mechanisms in thick and loose sandstone formations, we have carefully developed a coupled finite element numerical model that captures the complex interactions between fluid flow and solid deformation. This model is the cornerstone of our future exploration. Based on this model, the crack propagation problem of hydraulic fracturing under different engineering and geological conditions was studied. In addition, we conducted in-depth research on the key factors that shape the geometry of hydraulic fractures, revealing their subtle differences and complexities. It is worth noting that the sharp contrast between the stress profile and mechanical properties between the production layer and the boundary layer often leads to fascinating phenomena, such as the vertical merging of hydraulic fracture propagation. The convergence of cracks originating from adjacent layers is a recurring theme in these strata. Sensitivity analysis clarified our understanding, revealing that increased elastic modulus promotes longer crack propagation paths. As the elastic modulus increases from 12 GPa to 18 GPa, overall, the maximum crack width slightly decreases, with a less than 10% reduction rate. The increased fluid leakage rate will significantly shorten the length and width of hydraulic fractures (with a maximum decrease of over 70% in fracture width). The increase in viscosity of fracturing fluid causes a change in fracture morphology, with a reduction in length of about 32% and an increase in fracture width of about 25%. It is worth noting that as the leakage rate of fracturing fluid increases, the importance of the viscosity of fracturing fluid decreases relatively. Strategies such as increasing fluid viscosity or adding anti-filtration agents can alleviate these challenges and improve the efficiency of fracturing fluids. In summary, our research findings provide valuable insights that can provide information and optimization for hydraulic fracturing filling and fracturing strategies in loose sandstone formations, promoting more efficient and influential oil and gas extraction work.
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Cai, Minxi, Piaorong Xu, Bei Liu, Ziqi Peng, Jianhua Cai i Jing Cao. "A Threshold Voltage Model for AOS TFTs Considering a Wide Range of Tail-State Density and Degeneration". Electronics 11, nr 19 (30.09.2022): 3137. http://dx.doi.org/10.3390/electronics11193137.
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There have been significant differences in principle electrical parameters between amorphous oxide semiconductor (AOS) thin-film transistors (TFTs) and silicon-based devices for their distinct conduction mechanisms. Additionally, threshold voltage is one of the key parameters in device characterization and modeling. In this work, a threshold voltage model is developed for AOS TFTs considering the various density of exponential tail states below the conduction band, including degenerate conduction. The threshold condition is defined where the density ratio of free carriers to the trapped carriers reaches a critical value depending on the distribution parameters of tail states. The resulting threshold voltage expression is fully analytical and is of clear physical meaning, with simple parameter extraction methods. Numerical and experimental verifications show that this model provides appropriate values of threshold voltage for devices with different sub-gap tail states, which could be a useful method for identifying the threshold voltage of a large variety of AOS TFTs.
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Zhu, Mengge, Ji Zhang, Lingfan Bu, Sen Nie, Yu Bai, Yueqi Zhao i Ning Mei. "Methodology and Experimental Verification for Predicting the Remaining Useful Life of Milling Cutters Based on Hybrid CNN-LSTM-Attention-PSA". Machines 12, nr 11 (24.10.2024): 752. http://dx.doi.org/10.3390/machines12110752.
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In modern manufacturing, the prediction of the remaining useful life (RUL) of computer numerical control (CNC) milling cutters is crucial for improving production efficiency and product quality. This study proposes a hybrid CNN-LSTM-Attention-PSA model that combines convolutional neural networks (CNN), long short-term memory (LSTM) networks, and attention mechanisms to predict the RUL of CNC milling cutters. The model integrates cutting force, vibration, and current signals for multi-channel feature extraction during cutter wear. The model’s hyperparameters are optimized using a PID-based search algorithm (PSA), and comparative experiments were conducted with different predictive models. The experimental results demonstrate the proposed model’s superior performance compared to CNN, LSTM, and hybrid CNN-LSTM models, achieving an R2 score of 99.42% and reducing MAE, RMSE, and MAPE by significant margins. The results validate that the proposed method has significant reference and practical value for RUL prediction research of CNC milling cutters.
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Vorobyov, Maxim S., Tamara V. Koval, Nikolay N. Koval i Nguyen Bao Hung. "Generation, transport, and efficient extraction of a large cross-section electron beam into an air in an accelerator with a mesh plasma cathode". Laser and Particle Beams 36, nr 1 (17.01.2018): 22–28. http://dx.doi.org/10.1017/s0263034617000969.
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AbstractThe paper presents experimental and theoretical research data on the generation, transport, and extraction of a large cross-section (750 × 150 mm2) electron beam into the air through a thin metal foil in an accelerator with a mesh plasma cathode on the bases of a low-pressure arc and with a multi-aperture two-electrode electron-optical system. When the burning conditions of the arc discharge, responsible for the generation of the emission plasma, is changed, the characteristics of this plasma were investigated, including under the conditions of the selection of electrons from it. Our experiments show that at an accelerating voltage of 200 kV, current in the accelerating gap of up to 30 A, and full width at half maximum of up to 100 µm, the average extracted power is ≈4 kW and the extracted beam current is ≈85% from the common current into the accelerating gap. Our numerical estimates give a good correlation between the arc and emission plasma parameters depending on the electrode configuration in the discharge system and on the mechanism of electron beam generation. Analysis of the emission plasma parameters under different arc conditions and of the mechanisms responsible for the beam energy loss suggests that most of the energy in the accelerator is lost at the support grid and at the output foil due to defocusing of the beam and partial electron reflection from the foil. Other mechanisms that decrease the extracted beam energy are discussed.
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Garrigues, L., i G. Fubiani. "Tutorial: Modeling of the extraction and acceleration of negative ions from plasma sources using particle-based methods". Journal of Applied Physics 133, nr 4 (28.01.2023): 041102. http://dx.doi.org/10.1063/5.0128759.
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In this Tutorial, we consider plasma sources with applications to fusion devices and high energy accelerators. These ion sources typically produce negative ions from hydrogen-isotope gases, which are extracted through one or multiple apertures and accelerated to high kinetic energies. Next, they are either double stripped of two electrons to form positive ions used as precursors in accelerator devices or neutralized to produce a neutral beam injected in tokamak reactors. Contrary to the working conditions of most ion sources where volume production prevails, the mechanism of negative ion production by dissociative electron attachment on vibrationally excited molecules inside the plasma volume of fusion-type hydrogen-fueled high power discharges is mostly balanced by their destruction by detachment before being extracted rendering this means of producing negative ions rather inefficient. Surface production through the transfer of electrons from low work function metallic materials to the impacting atoms is the alternative solution to fulfill the requirements for the applications concerned. Negative ions are produced close to the aperture from which they are extracted. As a result, the analysis and understanding of the extraction mechanisms through experimental diagnostics is rather difficult due to the lack of accessibility and can only give a partial view. In addition, most of the experimental work is focused on the validation of requirements for the applications and not to the investigation of the fundamental processes that take place inside these types of sources. This Tutorial is focused on the description and understanding of the physical mechanisms behind the extraction and acceleration of negative ions from hydrogen plasma sources through modeling methods. We describe the numerical techniques of particle-based methods with a specific emphasis on particle-in-cell Monte Carlo collision algorithms. An analysis of the physical processes involved in driving the negative ions from the plasma source, across the apertures and inside the accelerator as reported in the literature, is presented in detail. This Tutorial concludes with additional and future works to be addressed in the coming years.
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Belardinelli, Maria Elina, Massimo Nespoli i Maurizio Bonafede. "Stress changes caused by exsolution of magmatic fluids within an axisymmetric inclusion". Geophysical Journal International 230, nr 2 (4.03.2022): 870–92. http://dx.doi.org/10.1093/gji/ggac093.
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SUMMARY In volcanic regions ascending magma is subject to depressurization and is generally accompanied by exsolution of volatiles. We assume a process in which these volatiles propagate upward across newly fractured and permeable rock layers, bringing a sharp increase of pore pressure and temperature within a thin disc-shaped region (inclusion). Thermo-poro-elastic (TPE) inclusion models provide a mechanism to explain seismicity and deformation induced by p and T changes in absence of new magma emplacement in volcanic contexts. They are also suitable to represent the mechanical effects due to fluid extraction and re-injection in geothermal fields. In the present work analytic solutions are provided for the displacement, strain and stress fields assuming a TPE unbounded medium. Significant deviatoric stress is generated by positive increments of pore pressure and temperature: the stress field is fully deviatoric outside the TPE inclusion, but a strong isotropic stress component is present within, leading to highly heterogeneous faulting mechanisms: if the disc plane is horizontal, thrust faulting mechanisms are favoured within the TPE disc over optimally oriented faults and normal mechanisms above. The model is easily generalized to a vertically thick disc with variable temperature and pore-pressure changes: then, an extensional environment can be obtained even within the TPE inclusion assuming upward decreasing of pore pressure and temperature changes. The supplied analytical solution may be used to model near-field TPE inclusion effects and to validate more complex numerical modelling.
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López-González, Mari Carmen, Gonzalo del Pozo, Diego Martín-Martín, Laura Muñoz-Díaz, José Carlos Pérez-Martínez, Enrique Hernández-Balaguera, Belén Arredondo, Yulia Galagan, Mehrdad Najafi i Beatriz Romero. "Evaluation of Active Layer Thickness Influence in Long-Term Stability and Degradation Mechanisms in CsFAPbIBr Perovskite Solar Cells". Applied Sciences 11, nr 24 (9.12.2021): 11668. http://dx.doi.org/10.3390/app112411668.
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Perovskite solar cells (PSCs) have become very popular due to the high efficiencies achieved. Nevertheless, one of the main challenges for their commercialization is to solve their instability issues. A thorough understanding of the processes taking place in the device is key for the development of this technology. Herein, J-V measurements have been performed to characterize PSCs with different active layer thicknesses. The solar cells’ parameters in pristine devices show no significant dependence on the active layer thickness. However, the evolution of the solar cells’ efficiency under ISOS-L1 protocol reveals a dramatic burn-in degradation, more pronounced for thicker devices. Samples were also characterized using impedance spectroscopy (IS) at different degradation stages, and data were fitted to a three RC/RCPE circuit. The low frequency capacitance in the thickest samples suffers a strong increase with time, which suggests a significant growth in the mobile ion population. This increase in the ion density partially screens the electric field, which yields a reduction in the extracted current and, consequently, the efficiency. This paper has been validated with two-dimensional numerical simulations that corroborate (i) the decrease in the internal electric field in dark conditions in 650 nm devices, and (ii) the consequent reduction in the carrier drift and, therefore, of the effective current extraction and efficiency.
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Qiu, Kaixuan, Kaifeng Fan, Xiaolin Chen, Gang Lei, Shiming Wei, Rahul Navik i Jia Li. "A New Approach for Production Prediction in Onshore and Offshore Tight Oil Reservoir". Journal of Marine Science and Engineering 11, nr 11 (30.10.2023): 2079. http://dx.doi.org/10.3390/jmse11112079.
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Rapid technological advances have accelerated offshore and onshore tight oil extraction to meet growing energy demand. Reliable tools to carry out production prediction are essential for development of unconventional reservoirs. The existed tri-linear analytical solutions are verified to be versatile enough to capture fundamental flow mechanisms and make accurate production predictions. However, these solutions are obtained in Laplace space with the Laplace transform and numerical inversion, which may lead to uncertainty in the solution. In this paper, a general analytical solution is derived in real-time space through integral transform and average pressure substitution. Namely, the partial differential equations describing subsurface fluid flow are firstly triple-integrated and then the obtained volume average pressure are replaced with the rate-dependent expressions. Furthermore, the ordinary differential equations related to oil rate are solved analytically in real-time space. To validate our model, this derived solution is verified against two numerical models constructed with two typical physical configurations. The great match indicates the accuracy and applicability of the analytical solution. According to the developed workflow, two field cases including offshore and onshore tight oilfield data are selected for history matching and production prediction. This new approach not only makes the obtained solution more simplified, but also helps field engineers diagnose flow patterns more quickly to better optimize production schemes.
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Zhang, Jianyong, Zhendong Cui, Xiaopeng Chen i Longfei Li. "Research Progress on the Microfracture of Shale: Experimental Methods, Microfracture Propagation, Simulations, and Perspectives". Applied Sciences 14, nr 2 (17.01.2024): 784. http://dx.doi.org/10.3390/app14020784.
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The fracture network generated by hydraulic fracturing in unconventional shale reservoirs contains numerous microfractures that are connected to macroscopic fractures. These microfractures serve as crucial pathways for shale gas to flow out from micro- and nano-scale pores, playing a critical role in enhancing shale gas recovery. Currently, more attention is being given by academia and industry to the evolution of macroscopic fracture networks, while the understanding of the microfracture mechanisms and evolution is relatively limited. A significant number of microfractures are generated during the hydraulic fracturing process of shale. These microfractures subsequently propagate, merge, and interconnect to form macroscopic fractures. Therefore, studying the fracture process of rock masses from a microscale perspective holds important theoretical significance and engineering value. Based on the authors’ research experience and literature review, this paper provides a brief overview of current progress in shale microfracture research from five aspects: in situ observation experiments of microfractures in shale, formation and evolution processes of discontinuous microfractures, the impact of inhomogeneity on microfracture propagation, measurement methods for microscale mechanical parameters and deformation quantities in shale, and numerical simulation of shale microfractures. This paper also summarizes the main challenges and future research prospects in shale microfracture studies, including: (1) quantitative characterization of in situ observation experimental data on shale microfractures; (2) formation and evolution laws of macroscopic, mesoscopic, and microscopic multi-scale discontinuous fractures; (3) more in-depth and microscale characterization of shale heterogeneity and its deformation and fracture mechanisms; (4) acquisition of shale micro-mechanical parameters; (5) refinement and accuracy improvement of the numerical simulation of microfractures in shale. Addressing these research questions will not only contribute to the further development of microfracture theory in rocks but also provide insights for hydraulic fracturing in shale gas extraction.
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Dghais, Wael, Malek Souilem, Fakhreddine Zayer i Abdelkader Chaari. "Power Supply- and Temperature-Aware I/O Buffer Model for Signal-Power Integrity Simulation". Mathematical Problems in Engineering 2018 (8.08.2018): 1–9. http://dx.doi.org/10.1155/2018/1356538.
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This paper presents the development and evaluation of a large-signal equivalent circuit model that accounts for the power supply fluctuation and temperature variation of I/O buffers circuit designed based on the fully depleted silicon on insulator (FDSOI) 28 nm process for signal-power integrity (SPI) simulation. A solid electrical analysis based on the working mechanisms of the nominal I/O buffer information specification- (IBIS-) like model is presented to support the derivation of an accurate and computationally efficient behavioral model that captures the essential effects of the power supply bouncing under temperature variation. The formulation and extraction of the Lagrange interpolating polynomial are investigated to extend the nominal equivalent circuit model. The generated behavioral model is implemented using the Newton-Neville’s formula and validated in simultaneous switching output buffers (SSO) scenario under temperature variation. The numerical results show a good prediction accuracy of the time domain voltage and current waveforms as well as the eye diagram of the high-speed communication I/O link while speeding-up the transient simulation compared to the transistor level model.
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Cerdeira, Ana T. S., João B. L. M. Campos, João M. Miranda i José D. P. Araújo. "Review on Microbubbles and Microdroplets Flowing through Microfluidic Geometrical Elements". Micromachines 11, nr 2 (15.02.2020): 201. http://dx.doi.org/10.3390/mi11020201.
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Two-phase flows are found in several industrial systems/applications, including boilers and condensers, which are used in power generation or refrigeration, steam generators, oil/gas extraction wells and refineries, flame stabilizers, safety valves, among many others. The structure of these flows is complex, and it is largely governed by the extent of interphase interactions. In the last two decades, due to a large development of microfabrication technologies, many microstructured devices involving several elements (constrictions, contractions, expansions, obstacles, or T-junctions) have been designed and manufactured. The pursuit for innovation in two-phase flows in these elements require an understanding and control of the behaviour of bubble/droplet flow. The need to systematize the most relevant studies that involve these issues constitutes the motivation for this review. In the present work, literature addressing gas-liquid and liquid-liquid flows, with Newtonian and non-Newtonian fluids, and covering theoretical, experimental, and numerical approaches, is reviewed. Particular focus is given to the deformation, coalescence, and breakup mechanisms when bubbles and droplets pass through the aforementioned microfluidic elements.
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De Boer, Wiebe P., Pieter C. Roos, Suzanne J. M. H. Hulscher i Ad Stolk. "AN IDEALIZED MODEL OF TIDAL DYNAMICS IN SEMI-ENCLOSED BASINS: THE EFFECTS OF A MEGA-SCALE SAND EXTRACTION TRENCH IN THE NORTH SEA". Coastal Engineering Proceedings 1, nr 32 (31.01.2011): 37. http://dx.doi.org/10.9753/icce.v32.currents.37.
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We investigate the effects of a mega-scale sand extraction trench (length ~200 km, width ~10 km, depth ~10 m, located in front of the Dutch coast) on tidal dynamics in the Southern North Sea. To this end, an idealized modeling approach is adopted, extending the classical problem of Kelvin wave reflection in rectangular semi-enclosed basins to account for lateral depth variations and the presence of a trench. The model results indicate changes in tidal range (zones of decrease and increase of the order of several cm), phase and currents (order cm/s) throughout the whole basin, which emphasizes the importance of a model domain on the scale of the basin. The changes in currents may structurally change sediment transport rates by several percents, which is relevant to coastal morphology. It is argued that this idealized model can be used to support a companion study carried out with a more detailed numerical engineering model. This is because of its ability to (1) provide insight into the physical mechanisms, (2) reveal the order of magnitude and area of influence of the effects and (3) allow for a quick sensitivity analysis with respect to trench geometry.
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Ortega Guerrero, Marcos Adrián. "Flujo de agua subterránea y transporte en medios geológicos fracturados: una revisión". Revista Mexicana de Ciencias Geológicas 41, nr 1 (26.03.2024): 103–29. http://dx.doi.org/10.22201/cgeo.20072902e.2024.1.1772.
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The groundwater flow and the transport of solutes and contaminants in fractured media play a very important role in various hydrogeological and geological processes. Fractures are discontinuities that occur in practically all types of rocks, consolidated and semi-consolidated sediments, in which it has interacted with the hydrological cycle at different scales of space and time. This article reviews 20 years of research in the CGEO of different selected examples in Mexico, from local to regional scales, associated with 1) Gravitational Groundwater Flow Systems, 2) The hydrogeochemical interaction of groundwater with fractured rocks through which it circulates, 3) Instrumentation and coupled numerical analysis of flow parameters and time-varying geomechanics, during consolidation associated with pumping, 4) Analysis of fracture generation with the development and application of coupled flow and geomechanical equations, 5) Formation of new minerals, 6) Sustenance of ecosystems, 7) Artificial fracturing of soils for their conservation and infiltration of rainwater improvement; and on the issue of transport in 8) Natural solute migration mechanisms, 9) Contaminants induced by pumping, 10) Spills of hydrocarbon derivatives in low permeability and double porosity media due to fracturing and 11) Heat. The results show the importance of fractured media in groundwater recharge in mountainous areas and flow towards granular media in quantity and quality, where residence times of a few years to thousands are involved, which implies modifying water and ecosystem management criteria, in the country; the complexity of these processes requires different methodologies for their evaluation, among them the instrumentation and calibration of numerical models from 1D to 3D for analysis, predictions and the proposal of restoration, sustainability and management solutions; they also help to prevent, control and mitigate the negative impacts on health and the environment caused by the induction of geogenic elements and by various types of pollutants; fractured media also support numerous terrestrial and marine ecosystems, and in the case of damaged agricultural soils, artificial fracturing allows increasing rainwater infiltration and improving productivity in adaptation to climate change and reducing the extraction in aquifers where safe capacity has been exceeded; unfortunately, excessive extraction in closed basins is causing fracturing of the aquitards, both hydraulic and due to differential settlement, which favors the migration of pore water rich in elements harmful to human health and the environment, whose natural function was its protection. All this requires designing mechanisms for the transfer of scientific knowledge to society and decision makers to propose novel restoration and sustainability strategies, under the new paradigm of Gravitational Groundwater Flow Systems.
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Xu, Wenjiang, Weidong Jiang, Yantao Xu i Bumin Guo. "Numerical Simulation Study on Dynamic Interaction between Two Adjacent Wells during Hydraulic Fracturing". Processes 12, nr 10 (24.09.2024): 2065. http://dx.doi.org/10.3390/pr12102065.
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The heterogeneity in fracture formation significantly influences the hydraulic fracture propagation among adjacent wells, underscoring the urgency to comprehend the underlying fracture mechanisms. Specifically, in shale gas or oil extraction fracturing operations, stress interactions among neighboring fracturing clusters, or mutual interference during the propagation of parallel fractures, are commonplace. At present, there is relatively little research on the sensitivity parameters of adjacent borehole fracture propagation morphology. Consequently, we employed ABAQUS software 2022 to construct a numerical model simulating the fracturing of adjacent boreholes in opposing directions. Upon validating the model’s fidelity, we systematically explored the influence of various engineering and geological factors on fracture morphology and propagation length. Our findings revealed a three-phase evolution: independent fracture propagation, subsequent mutual repulsion, and, ultimately, mutual attraction. It is worth noting that increasing the elastic modulus from 10 GPa to 80 GPa, and increasing the crack length by 16.30%, is beneficial for crack propagation, while the horizontal stress difference profoundly shapes the crack mode, but has a relatively small impact on the overall crack length. When HSD increases from 0 MPa to 15 MPa, the total crack length only changes by 1.24%. In addition, the filtration coefficient of the reservoir is a key determining factor that has a significant impact on the morphology and length of cracks generated by adjacent boreholes. Increasing the filtration coefficient from 1 × 10−14 m3/s/Pa to 5 × 10−12 m3/s/Pa reduces the total length of cracks by 60.77%. Notably, an optimal injection rate exists, optimizing fracturing outcomes. Conversely, the viscosity of the fracturing fluid exerts a limited influence on fracture morphology and length within the confines of this simulation, allowing for the selection of a suitable viscosity to ensure smooth proppant transport during actual fracturing operations. In designing fracturing parameters, it is imperative to aim for sufficient fracture propagation length while harnessing “stress interference” to foster the development of intricate fracture networks. Ultimately, our research findings serve as a solid foundation for engineering practices involving hydraulic fracture propagation in adjacent boreholes undergoing opposing fracturing operations.
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Montes Rivera, Martín, Carlos Guerrero-Mendez, Daniela Lopez-Betancur i Tonatiuh Saucedo-Anaya. "Dynamical Sphere Regrouping Particle Swarm Optimization Programming: An Automatic Programming Algorithm Avoiding Premature Convergence". Mathematics 12, nr 19 (27.09.2024): 3021. http://dx.doi.org/10.3390/math12193021.
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Symbolic regression plays a crucial role in machine learning and data science by allowing the extraction of meaningful mathematical models directly from data without imposing a specific structure. This level of adaptability is especially beneficial in scientific and engineering fields, where comprehending and articulating the underlying data relationships is just as important as making accurate predictions. Genetic Programming (GP) has been extensively utilized for symbolic regression and has demonstrated remarkable success in diverse domains. However, GP’s heavy reliance on evolutionary mechanisms makes it computationally intensive and challenging to handle. On the other hand, Particle Swarm Optimization (PSO) has demonstrated remarkable performance in numerical optimization with parallelism, simplicity, and rapid convergence. These attributes position PSO as a compelling option for Automatic Programming (AP), which focuses on the automatic generation of programs or mathematical models. Particle Swarm Programming (PSP) has emerged as an alternative to Genetic Programming (GP), with a specific emphasis on harnessing the efficiency of PSO for symbolic regression. However, PSP remains unsolved due to the high-dimensional search spaces and local optimal regions in AP, where traditional PSO can encounter issues such as premature convergence and stagnation. To tackle these challenges, we introduce Dynamical Sphere Regrouping PSO Programming (DSRegPSOP), an innovative PSP implementation that integrates DSRegPSO’s dynamical sphere regrouping and momentum conservation mechanisms. DSRegPSOP is specifically developed to deal with large-scale, high-dimensional search spaces featuring numerous local optima, thus proving effective behavior for symbolic regression tasks. We assess DSRegPSOP by generating 10 mathematical expressions for mapping points from functions with varying complexity, including noise in position and cost evaluation. Moreover, we also evaluate its performance using real-world datasets. Our results show that DSRegPSOP effectively addresses the shortcomings of PSO in PSP by producing mathematical models entirely generated by AP that achieve accuracy similar to other machine learning algorithms optimized for regression tasks involving numerical structures. Additionally, DSRegPSOP combines the benefits of symbolic regression with the efficiency of PSO.