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Artykuły w czasopismach na temat "Numerical Extraction Mechanisms"
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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.
Rozprawy doktorskie na temat "Numerical Extraction Mechanisms"
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Chapalain, Thomas. "Investigating the representation of numerosity in humans and convolutional neural networks using high-variability photorealistic stimuli". Electronic Thesis or Diss., université Paris-Saclay, 2025. http://www.theses.fr/2025UPASG020.
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La capacité à estimer rapidement le nombre d'éléments dans une scène sans compter explicitement a fait l'objet de nombreuses recherches.Les études expérimentales et les modèles computationnels ont cherché à révéler les mécanismes permettant au cerveau humain de percevoir la numérosité d'un seul coup d'œil. Les récentes avancées en imagerie, incluant l'IRM fonctionnelle, l'analyse multivariée et la modélisation du champ récepteur des neurones, ont permis d'en apprendre davantage sur la manière dont l'information numérique est encodée dans le cerveau. En particulier, ces travaux ont mis en lumière le rôle de régions telles que les cortex frontal et pariétal dans la perception numérique. Malgré ces avancées, la recherche sur la perception de la numérosité a souvent reposé sur des stimuli visuels simplifiés. Bien que pratiques, ces stimuli ne reflètent pas la complexité des environnements visuels réels et négligent souvent l'impact de leurs statistiques non numériques, qui covarient pourtant avec la numérosité. Cette dépendance soulève des questions sur la validité écologique des résultats actuels et questionne si la numérosité est une propriété perçue directement ou inférée à partir d'autres caractéristiques visuelles. Les mécanismes sous-jacents à la perception visuelle de la numérosité restent donc une question ouverte. Dans cette thèse, nous avons développé un ensemble de stimuli synthétiques photoréalistes afin de pallier ces limites. Ces stimuli présentent une grande variabilité visuelles tout en permettant un contrôle expérimental précis. Ce jeu de données permet d'étudier la perception de la numérosité dans des contextes plus proches des images naturelles. À l'aide de ces stimuli photoréalistes, constitués d'objets 3D intégrés dans des scènes variées, nos analyses ont montré que les réseaux de neurones convolutifs profonds (CNN) optimisés pour la reconnaissance d'objets peuvent encoder des informations numériques dans divers contextes. À l'inverse, les réseaux non entraînés ne parviennent pas à discriminer le contenu numérique, se limitant à encoder des statistiques visuelles de bas niveau. Ces résultats indiquent que les modèles non entraînés sont inadaptés pour comprendre notre capacité à extraire le contenu numérique d'une scène et soulignent l'importance d'utiliser des stimuli complexes pour étudier la représentation de la numérosité. Étant donné le rôle des CNN en tant que modèles de la voie visuelle ventrale, nous avons ensuite exploré la représentation numérique au-delà des régions dorsales traditionnelles. Ainsi, nous avons enregistré l'activité cérébrale de participants portant leur attention sur le contenu numérique de nos stimuli visuels photoréalistes. Ce paradigme expérimental a permis de dissocier l'information numérique des statistiques visuelles corrélées, et ainsi d'examiner leurs contributions distinctes. Nos résultats ont révélé que les zones occipito-latérales, souvent associées à la reconnaissance d'objets, peuvent traiter simultanément des informations numériques et liées aux objets. De plus, les régions pariétales ont démontré un rôle spécialisé dans l'encodage de l'information numérique. En revanche, les statistiques visuelles de bas niveau influencent principalement les régions visuelles primaires et ventrales temporales, avec un impact minimal sur les régions dorsales supérieures. Ces résultats soulignent l'existence d'une organisation hiérarchique dans le traitement visuel, avec une progression de l'encodage de caractéristiques élémentaires à la représentation abstraite d'objets et de la numérosité dans les régions avancées du cerveau. Nos travaux mettent en lumière la nature abstraite de la représentation de la numérosité et approfondissent ainsi notre compréhension de la cognition numérique dans des environnements visuels réalistes. Ils soulignent également l'importance d'utiliser des stimuli complexes pour découvrir les mécanismes sous-jacents à l'extraction de la numérosité dans le cerveauThe ability to rapidly estimate the number of items in a scene without explicit counting, known as visual number sense, has been the focus of extensive research. Experimental studies and computational models have sought to uncover the mechanisms that enable the human brain to extract numerosity at a glance. Recent advances in imaging techniques, including ultra-high-field functional MRI (fMRI), multivariate pattern analysis, and population receptive field (pRF) modeling, have provided deeper insights into how numerical information is encoded in the brain.These studies have highlighted the involvement of higher-order regions, such as the frontal and parietal cortices, but also lower-level areas, in numerical perception. Most research on numerosity perception has relied on simplified visual stimuli, such as binary dot arrays. While useful, these stimuli fail to capture the complexity of real-world visual environments and present a special case where numerosity is tightly correlated with some low-level statistics of the visual input. This raises questions about ecological validity, and about the extent to which previous findings reflected the discrete number of items per se as opposed to correlated low-level factors. In this thesis, we developed a synthetic photorealistic stimulus dataset to address these limitations, introducing high variability in the characteristics of both objects and scenes while maintaining precise experimental control. This dataset allows for the study of numerosity perception in contexts closer to natural images. Using this new dataset of photorealistic renderings of 3D objects embedded in diverse background scenes, our analyses demonstrated that deep convolutional neural networks (CNNs) optimized for object recognition could encode numerical information with robustness to diverse objects and scenes in distributed activity patterns of their higher convolutional layers. Conversely, untrained networks failed to discriminate numerical content across changes in those other high-level visual properties and mainly encoded low-level summary statistics.These findings suggest that untrained models may not truly encode discrete numerosity and emphasize the importance of using complex stimuli to probe the neural mechanisms of visual number sense. Given the role of CNNs' as models of the ventral visual stream, this research motivates further investigation of how numerical information is represented in the brain beyond commonly studied dorsal-parietal areas. Therefore, in an independent 7T fMRI study, we recorded brain activity of both ventral and dorsal visual pathways while participants viewed and attended to the numerical content of similar synthetic photorealistic stimuli.This experimental paradigm enabled us to disentangle numerical information from correlated visual statistics, allowing for the examination of their distinct contributions to brain activity. Our findings revealed that lateral occipital areas, commonly linked to object recognition, could simultaneously represent numerical and object-related information. Additionally, dorsal parietal regions demonstrated a specialized role in encoding numerical information beyond basic visual features. In contrast, low-level visual statistics primarily influenced early visual and higher-level ventral temporal areas, with minimal impact on higher-order dorsal regions. These findings illustrate a hierarchical organization in visual processing, transitioning from encoding of low-level features to more invariant representations of objects and numerosity in higher-level brain areas. Our work underscores the abstract nature of numerosity representations, advancing our understanding of numerical cognition under more realistic visual conditions
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Bylin, Johan. "Best practice of extracting magnetocaloric properties in magnetic simulations". Thesis, Uppsala universitet, Materialteori, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-388356.
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In this thesis, a numerical study of simulating and computing the magnetocaloric properties of magnetic materials is presented. The main objective was to deduce the optimal procedure to obtain the isothermal change in entropy of magnetic systems, by evaluating two different formulas of entropy extraction, one relying on the magnetization of the material and the other on the magnet's heat capacity. The magnetic systems were simulated using two different Monte Carlo algorithms, the Metropolis and Wang-Landau procedures. The two entropy methods proved to be comparably similar to one another. Both approaches produced reliable and consistent results, though finite size effects could occur if the simulated system became too small. Erroneous fluctuations that invalidated the results did not seem stem from discrepancies between the entropy methods but mainly from the computation of the heat capacity itself. Accurate determination of the heat capacity via an internal energy derivative generated excellent results, while a heat capacity obtained from a variance formula of the internal energy rendered the extracted entropy unusable. The results acquired from the Metropolis algorithm were consistent, accurate and dependable, while all of those produced via the Wang-Landau method exhibited intrinsic fluctuations of varying severity. The Wang-Landau method also proved to be computationally ineffective compared to the Metropolis algorithm, rendering the method not suitable for magnetic simulations of this type.
Części książek na temat "Numerical Extraction Mechanisms"
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Schulz, H., C. Schwab i W. L. Wendland. "An Extraction Technique for Boundary Element Methods". W Notes on Numerical Fluid Mechanics (NNFM), 219–31. Wiesbaden: Vieweg+Teubner Verlag, 1996. http://dx.doi.org/10.1007/978-3-322-89941-5_18.
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Baysal, Kudret, Tobias Schafhitzel, Thomas Ertl i Ulrich Rist. "Extraction and Visualization of Flow Features". W Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 305–14. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-01106-1_30.
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Shen, Lawrence K., i An-Nan Chien. "Numerical Solution and Extraction of Design Parameter Curves for a Nonlinear Dynamic System". W Computational Mechanics ’88, 1168–69. Berlin, Heidelberg: Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/978-3-642-61381-4_310.
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Chemnitz, Alexander, i Thomas Sattelmayer. "Calculation of the Thermoacoustic Stability of a Main Stage Thrust Chamber Demonstrator". W Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 235–47. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-53847-7_15.
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Abstract The stability behavior of a virtual thrust chamber demonstrator with low injection pressure loss is studied numerically. The approach relies on an eigenvalue analysis of the Linearized Euler Equations. An updated form of the stability prediction procedure is outlined, addressing mean flow and flame response calculations. The acoustics of the isolated oxidizer dome are discussed as well as the complete system incorporating dome and combustion chamber. The coupling between both components is realized via a scattering matrix representing the injectors. A flame transfer function is applied to determine the damping rates. Thereby it is found that the procedure for the extraction of the flame transfer function from the CFD solution has a significant impact on the stability predictions.
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Lacroix, Zoé, Arnaud Sahuguet i Raman Chandrasekar. "Information extraction and database techniques: A user-oriented approach to querying the web". W Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 289–304. Cham: Springer International Publishing, 1998. http://dx.doi.org/10.1007/bfb0054231.
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Send, Wolfgang. "Stroke-Wing Engine with Dual Wings for Extracting Power from an Airstream". W Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 883–94. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-27279-5_77.
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Schollenberger, Michael, i Thorsten Lutz. "Comparison of Different Methods for the Extraction of Airfoil Characteristics of Propeller Blades as Input for Propeller Models in CFD". W Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 24–34. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-79561-0_3.
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Carrigan, Tobias D., i James P. Talbot. "Extracting Information from Axle-Box Acceleration: On the Derivation of Rail Roughness Spectra in the Presence of Wheel Roughness". W Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 286–94. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-70289-2_29.
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Solazzi, Luigi, i Nicola Pellegrini. "Design and Numerical Study of a 2-DoF Mechanism for Efficient Wave Energy Extraction in Onshore Application". W Proceedings of I4SDG Workshop 2021, 3–11. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-87383-7_1.
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Xie Shejuan, Tian Mingming, Pei Cuixiang, Chen Hong-En, Chen Zhenmao i Takagi Toshiyuki. "Composite Defects Evaluation Using the Hybrid NDT Methods of PECT and EMAT". W Studies in Applied Electromagnetics and Mechanics. IOS Press, 2017. https://doi.org/10.3233/978-1-61499-767-2-139.
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In this paper, a hybrid nondestructive testing (NDT) method combined with the pulsed eddy current testing (PECT) method and the electromagnetic acoustic transducer (EMAT) method has been proposed and validated through numerical simulations and experiments. First, a numerical code is developed for the simulation of hybrid EMAT/PECT signals. Second, based on the numerical simulation, the influences of the eddy current induced by the excitation coil and the eddy current due to the velocity effect of the ultrasonic wave are compared and analyzed. Third, several signal separation and extraction methods are proposed on the basis of the spectral analysis and filtering strategies. Finally, hybrid EMAT/PECT experiments are conducted. Based on the numerical and experimental results, the proposed hybrid PECT/EMAT NDT method is demonstrated both high detectability and high efficiency.
Streszczenia konferencji na temat "Numerical Extraction Mechanisms"
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Bataee, M., M. C. Chai, Z. Bennour, R. Carter, Z. Hamdi i A. M. Hassan. "CO2-Driven Geothermal Energy Extraction in the Baram Basin, Sarawak: Insights from Numerical Reservoir Simulations". W SPE Conference at Oman Petroleum & Energy Show. SPE, 2024. http://dx.doi.org/10.2118/218756-ms.
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Abstract This progress report focuses on the potential for geothermal energy extraction in Malaysia, particularly in the Sabah and Sarawak sedimentary basins. Despite the region's rich deep reservoirs, development in this area has been limited. Our study emphasizes the extraction of geothermal energy from the Sarawak Basin's geothermal reservoirs through CO2 injection. We primarily investigate sandstone formations, analyzing their properties and the feasibility of hot water extraction using CO2. The report provides a theoretical framework to understand the primary recovery mechanisms for fluid extraction from these reservoirs. To simulate geothermal reservoir performance, a commercial reservoir simulator was used. Due to the lack of precise data, our analysis relies on existing literature and estimations, which are substantiated by relevant sources to ensure reliability. We constructed a reservoir model to compare scenarios with and without CO2 injection, demonstrating that CO2 injection significantly enhances energy extraction. Our findings also suggest that sandstone formations can effectively trap CO2, offering a dual benefit of permanent underground storage and improved fluid production from the reservoir. Lastly, the report identifies areas for further improvement in this field.
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Piya, Cecil, Indraneel Sircar, James D. Van de Ven i David J. Olinger. "Numerical Modeling of Liquid Piston Gas Compression". W ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-10621.
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Prior research has shown that the use of liquid-pistons in place of conventional solid pistons within gas compression technologies can significantly improve the efficiency of gas compression. The liquid-piston provides the prospect for a consistent and high rate of heat extraction from the compressed gas during system operation. Consequently, the input power requirements during each individual compression are lowered. To validate this concept, analytical studies of the thermal-fluids and heat transfer mechanisms during gas compression were performed. The analysis involved the development of a numerical model, using the finite-difference method, which simulated a single compression stroke and quantified the crucial parameters during compression. This model was utilized to obtain theoretical efficiency values and to recognize optimal system characteristics. The results obtained from the simulation indicated double-digit increase in efficiency with the introduction of the liquid-piston.
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Eremin, M. O., A. Yu Peryshkin, L. D. Pavlova i V. N. Fryanov. "Numerical assessment of the stability of security pillars during the development of adjacent extraction columns of an inclined seam". W Physical Mesomechanics of Materials. Physical Principles of Multi-Layer Structure Forming and Mechanisms of Non-Linear Behavior. Novosibirsk State University, 2022. http://dx.doi.org/10.25205/978-5-4437-1353-3-173.
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Masud, Nahian, i Chris Qin. "Numerical Study on Semi-Active Flapping Hydrofoils for Energy Extraction Using Overset Mesh". W ASME 2024 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2024. https://doi.org/10.1115/imece2024-147330.
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Abstract The exploitation of flapping hydrofoils presents a promising avenue for harnessing hydrokinetic energy in riverine and tidal environments. Unlike traditional rotational mechanisms, flapping hydrokinetic devices offer several advantages, including simpler foil geometries, reduced structural demands, improved hydrodynamic performance, suitability for shallow waters, and lower impacts on aquatic ecosystems. While previous numerical studies have mainly focused on hydrofoils with fully prescribed motions, this research introduces a semi-active strategy that allows the heaving motion of a NACA0012 hydrofoil to respond passively to the hydrodynamic forces, while maintaining prescribed pitching. The simulations were conducted at a Reynolds number of 3.6 × 105, representing practical conditions for efficient energy extraction. Two-dimensional (2D) unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations are implemented and validated with experimental data. The overset mesh interface provides improved control over the meshing for the hydrofoil’s pitching and heaving compared to traditional dynamic mesh approaches, which require mesh regeneration. A user-defined function (UDF) is utilized to model the pitching and dynamically predict the heaving motions based on the hydrodynamic forces exerted on the foil. Importantly, this UDF enables the dynamic modeling of power take-off systems to directly predict power generation, including aspects such as generator torque and rotational speed. This study offers new insights into the non-sinusoidal angle of attack dynamics across various operational pitching frequencies and reveals that higher pitching frequencies can result in increased normal forces and enhanced heaving motion. The results not only enhance understanding of heaving motion dynamics but also hold significant implications for the design and optimization of hydrokinetic systems in terms of environmental compatibility and energy efficiency.
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Esmaeili, Sajjad, Seyed Emad Siadatifar, Mohammad Mesbah, Brij Maini i Apostolos Kantzas. "Experimental and Numerical Study of Asphaltene Deposition and Precipitation in the Vapor Extraction Process". W SPE Canadian Energy Technology Conference and Exhibition. SPE, 2023. http://dx.doi.org/10.2118/212769-ms.
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Abstract Vapor Extraction (VAPEX) is one of the most promising solvent-based methods to tackle the issues associated with SAGD. Asphaltene precipitation due to solvent injection and its in-situ upgrading plays an essential role in VAPEX. As the VAPEX chamber expands laterally and vertically, the speed of the front movement and the angle of the chamber boundary varies. This research investigates the rate of asphaltene precipitation and deposition in VAPEX using different solvents. In this research, three VAPEX experiments are carried out in a physical model using bitumen and three solvents (propane, butane, and pentane), where VAPEX chamber movement, expansion rate, and the amount of precipitated asphaltenes are monitored. In addition, an Eulerian-Lagrangian model, including the Eulerian approach for the continuous phase (solvent-rich area of the chamber) and the Lagrangian approach for the extracted asphaltene solid particles by bitumen dilution, is generated for numerical modelling. The movement and the deposition of the asphaltene particles at the front are calculated and then validated with the physical model experiments. A significant amount of precipitated asphaltenes was observed when pentane was used, as it creates a pattern on the wall of the physical model, especially near the wellbore area. However, no specific pattern was observed for other experiments. In terms of chamber expansion and movement, the chamber expanded laterally and then vertically in the pentane and propane systems, while the butane system revealed vertical movement at the beginning, followed by lateral movement. In all cases, the amount of precipitated asphaltenes was always higher near the wellbore compared with areas far from the production well. A numerical model has been implemented to capture the transport phenomena, simulate the asphaltene deposition mechanisms, and reveal the variations in the behavior of different solvents. This study can assist the oil sands industry in optimizing the VAPEX process to have an effective in-situ upgrading and the highest production rate with better oil API gravity, as the literature suffers from a lack of understanding of the mass transfer physics involved in VAPEX. Also, this study sheds light on the physics behind the asphaltene deposition and precipitation process in VAPEX, as it is impossible to be understood without molecular dynamic simulation besides laboratory experiments.
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Jian, Wu, Zhou Libo, Jiang Yao, Wang Yun, Yang Qi, Qian Chunjiang, Zhang Cheng i in. "Experimental and Numerical Investigation on Fracture Propagation Sensitivity Parameters in Deep Coal Seams". W 58th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2024. http://dx.doi.org/10.56952/arma-2024-0917.
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ABSTRACT: Hydraulic fracturing is the primary method for increasing hydrocarbon production in the extraction of deep coal bed methane. Understanding the initiation and propagation mechanisms of hydraulic fractures in deep coal seams, as well as developing design principles for hydraulic fracturing operations, can improve the efficiency of such operations. This study aims to identify the key factors affecting hydraulic fracture initiation and propagation in deep coal seams through indoor experiments and numerical simulations of deep coal seam wells. The study conducted an indoor experiment on hydraulic fracturing, using CT three-dimensional reconstruction technology and a two-dimensional fractal dimension analysis method to analyze the fracture morphology of deep coal seams. The study assessed the impact of various parameters, including fracturing displacement, fracturing fluid viscosity, lithology, and well trajectory, on hydraulic fracture initiation and fracture propagation. Additionally, a numerical model of fracture propagation was established to simulate hydraulic fracture initiation and propagation in typical wells in deep coal seams. The study also employed a two-dimensional fractal dimension analysis method and weight analysis method to analyze sensitivity parameters affecting fracture complexity and identified the main controlling factors of fracture initiation and propagation in deep coal seams. This study explores the basic principles of complex fracture propagation mechanisms through small-scale indoor hydraulic fracturing experiments. It aims to identify the key operational parameters that can enhance the complexity of fracture networks in hydraulic fracturing. The study also uses numerical simulations to analyze the important factors that influence the complexity of fractures through well-scale numerical simulations of fracture propagation. This approach provides design tools and theoretical insights for optimizing hydraulic fracturing design in deep coal seams. 1. INTRODUCTION Coalbed methane is an unconventional oil and gas resource. More than 47.6 trillion cubic meters of coalbed methane resources exist in coal reservoirs buried at a depth of more than 1500 meters (Zuo H.C, 2015). Coal seams have a unique bedding and cutting development system and usually require hydraulic fracturing methods to obtain a high yield. Deep coal seams have poor physical properties, high stress, low permeability, and strong adsorption capacity, so the effect of conventional fracturing transformation is not acceptable.
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Su, Wei, Zhiliang Wang, Miao Li i Linfang Shen. "The Coupling Mechanisms of Seepage and Heat Transfer in Rock Fractures in Enhanced Geothermal Systems Based on the Lattice Boltzmann Method". W ASME 2024 43rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2024. http://dx.doi.org/10.1115/omae2024-130931.
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Abstract The coupling mechanism of seepage and heat transfer in high-temperature rock fractures controls the heat extraction ability of enhanced geothermal systems. Utilising the lattice Boltzmann method, a numerical model is proposed to capture this coupling, accounting for fluid temperature’s influence on kinematic viscosity and thermal diffusion coefficient in rough fractures. The model’s validity is confirmed through a classic example. The effect of rough fracture surface on the coupling mechanism of seepage and heat transfer was analysed. The relationship between the roughness of the fracture surface and the performance indicators of geothermal extraction was discussed. The results show that neglecting the roughness of the fracture surface would lead to a severe underestimation of water temperatures within the fractures. As the roughness of the fracture surface intensified, its thermal breakthrough time gradually increased while the heat recovery rate and heat production power decreased.
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Moreira, Debora C., Gherhardt Ribatski i Satish G. Kandlikar. "Review of Enhancement Techniques With Vapor Extraction During Flow Boiling in Microchannels". W ASME 2020 18th International Conference on Nanochannels, Microchannels, and Minichannels collocated with the ASME 2020 Heat Transfer Summer Conference and the ASME 2020 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icnmm2020-1068.
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Abstract Flow boiling heat transfer in microchannels can remove high heat loads from restricted spaces with high heat transfer coefficients and minimum temperature gradients. However, many works still report problems with instabilities, high pressure drop and early critical heat flux, which hinder its possible applications as thermal management solutions. Much comprehension on the phenomena concerning flow boiling heat transfer is still missing, therefore many investigations rely on empirical methods and parametric studies to develop novel configurations of more efficient heat sinks. Nevertheless, investigations involving vapor extraction have successfully addressed all these previously reported issues while also increasing the heat transfer of heat sinks employing flow boiling in microchannels. In this sense, the objective of this review is to identify the main techniques employed for vapor extraction in microchannels-based heat sinks and analyze the physical mechanisms underneath the observed improvements during flow boiling, such that some design guidelines can be drawn. Three main strategies can be identified: passive vapor extraction, active vapor extraction, and membrane-based vapor extraction. All these strategies were able to dissipate heatfluxes higher than 1 kW/cm2, with the best performance achieved by a membrane-based heat sink, followed by active and passive designs. According to the present experimental and numerical data available in the literature, there is still room for improvement.
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Liu, Rui, Xuelin Dong i Deli Gao. "Numerical Simulation of Enhancing Coalbed Methane Recovery by RF Heating with Small Spacing Well Pattern". W 58th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2024. http://dx.doi.org/10.56952/arma-2024-0087.
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ABSTRACT: In recent years, electromagnetic (EM) heating excitation technology has been widely concerned in the exploitation of Coalbed methane (CBM). However, the heating volume of a single antenna in a vertical well is limited and cannot meet the needs of large-scale development. From the perspective of multi-well and multi-antenna, this paper establishes a mathematical model of radio frequency (RF) heating coupled with EM field and temperature field of small-spacing well pattern, comprehensively analyzes the average temperature and heating efficiency of coal seam heated by RF, reveals the influence law of different well types on the temperature distribution of coal seam, and conducts sensitivity analysis on heating power, well spacing and well pattern layout according to the characteristics of well pattern. The results show that triangular well pattern heating has higher heating efficiency and heating rate. Increasing the RF heating power can improve the heating rate and heating range of the coal seam, but too high power will form high temperatures near the wellbore, resulting in downhole equipment or wellbore integrity failure. On the whole, the spacing of heating wells has little effect on the average temperature of coal seam. The larger the spacing of wells in 5 ∼ 9 m, the larger the heating range, but the worse the superposition effect of temperature. Finally, according to the different well pattern layout schemes in the same reservoir, the optimal scheme is well pattern 1. 1. INTRODUCTION CBM is a kind of unconventional gas in coal seams. Deep coal seam has the characteristics of low formation pressure, low permeability and weak gas saturation, which are the biggest challenges faced by coalbed gas exploitation (Gao et al., 2022). To overcome these challenges, engineers and researchers have proposed a number of methods, such as hydraulic fracturing, blasting, partial pyrolysis, solvent extraction, inert gas displacement, etc. (Guo et al., 2020). These methods can be divided into two categories: decompression and anti-reflection mechanisms. However, these approaches face environmental and economic challenges. In recent years, thermal stimulation technology has been widely concerned as an alternative method to increase natural gas production in unconventional reservoirs.
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Dang, Yike, Zheng Yang, Shangtong Yang i Junlong Shang. "Thermal Damage in Crystalline Rocks: The Role of Heterogeneity in Mechanical Performance and Fracture Mechanisms". W 58th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2024. http://dx.doi.org/10.56952/arma-2024-0106.
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ABSTRACT: Investigating thermally treated rocks' mechanical properties and failure processes is crucial for advancing geothermal energy storage and extraction technologies. Naturally occurring rocks typically exhibit inherent flaws and fractures. Nevertheless, existing studies on the impact of thermal treatment on rock damage predominantly utilize intact rock specimens, either through numerical simulations or experimental approaches. This research introduces the Grain-Based model (GBM) to represent the complex shapes of mineral grains accurately and incorporates the heterogeneity of grain sizes. By employing the Weibull distribution, the model captures the variability in rock internal strength due to microcracks, porosity, mineral composition, and other factors. Furthermore, it integrates the temperature dependency of rocks' physical and mechanical properties when subjected to elevated temperatures, the numerical simulation reproduced the phenomenon that the compaction stage of the stress-strain curve caused by thermal damage extends as the temperature rises. Overall, this study provides a complete understanding of the thermal effects on rock integrity. 1. INTRODUCTION Rocks in nature commonly contain defects such as joints, fissures, and structural planes, which have a decisive impact on the mechanical behavior and stability of the rocks. Particularly under conditions of high temperature, the mechanical properties and failure mechanisms of rocks with such defects can vary significantly from those observed at room temperatures, thus impacting the safety and reliability of rock engineering projects. In geological engineering, nuclear waste storage, and geothermal energy development, rocks are routinely subjected to high-temperature environments. Temperature variations can intensify the expansion of internal defects in rocks, modify their mechanical attributes, and trigger new failure modes. As a quintessential crystalline rock, granite possesses a markedly heterogeneous internal structure. This heterogeneity leads to unique thermal stress responses and failure mechanisms under high temperature and stress conditions, which are significantly different from those observed in homogeneous materials. The non-uniform thermal expansion can result in substantial stress concentration within the rock, facilitating the initiation and propagation of cracks. This process, in turn, impacts engineering structures' long-term performance and reliability.