Now showing items 1-20 of 54906

    • KAUST Library Transformative Agreements 2019 2021

      Tomic, Nevena; Alsaedi, Yasmeen; Zibani, Patiswa (2021-09-28) [Poster]
      The Kaust University Library signed a number of transformative agreements with STEM publishers from 2019 to 2021. This poster presents our initial strategy, results, challenges, and plans in the open access publishing area. In 2019 KAUST Library signed 3 transformative agreements with STEM publishers. In 2020 the number of deals increased to 7, and in 2021 to 11. The number of OA articles published under these agreements has been growing steadily - 31 articles published under the terms of transformative agrements in 2019, 111 articles in 2020. The expectations of KAUST authors to have more options to publish open access free of charge are growing, too. Our initial strategy proved to be very successful with smaller and mid-sized publishers, but we reached the point where we should create an evidence-based approach and revise our strategy to deal with big publishers. Higher instances and alignment with the University-wide strategic plan (with clear goals in open research and open access area) are needed to take our open access publishing to the next level.
    • Droplet lift-off from hydrophobic surfaces from impact with soft-hydrogel spheres

      Truscott, T. T.; Rabbi, Rafsan; Kiyama, Akihito; Allen, John (KAUST Research Repository, 2021-09-19) [Dataset]
    • RNA-Sequencing And Mass-Spectrometry Proteomic Time-Series Analysis of T-Cell Differentiation Identified Multiple Splice Variants Models That Predicted Validated Protein Biomarkers In Inflammatory Diseases

      Magnusson, Rasmus; Rundquist, Olof; Kim, Min Jung; Hellberg, Sandra; Na, Chan Hyun; Benson, Mikael; Gomez-Cabrero, David; Kockum, Ingrid; Tegner, Jesper; Piehl, Fredrik; Jagodic, Maja; Mellergård, Johan; Altafini, Claudio; Ernerudh, Jan; Jenmalm, Maria C.; Nestor, Colm E.; Kim, Min-Sik; Gustafsson, Mika (Research Square Platform LLC, 2021-09-17) [Preprint]
      Background Profiling of mRNA expression is an important method to identify biomarkers but complicated by limited correlations between mRNA expression and protein abundance. We hypothesized that these correlations could be improved by mathematical models based on measuring splice variants and time delay in protein translation. Methods We characterized time-series of primary human naïve CD4+ T cells during early T-helper type 1 differentiation with RNA-sequencing and mass-spectrometry proteomics. We then performed computational time-series analysis in this system and in two other key human and murine immune cell types. Linear mathematical mixed time-delayed splice variant models were used to predict protein abundances, and the models were validated using out-of-sample predictions. Lastly, we re-analysed RNA-Seq datasets to evaluate biomarker discovery in five T-cell associated diseases, further validating the findings for multiple sclerosis (MS) and asthma.Results The new models significantly out-performing models not including the usage of multiple splice variants and time-delays, as shown in cross-validation tests. Our mathematical models provided more differentially expressed proteins between patients and controls in all five diseases. Moreover, analysis of these proteins in asthma and MS supported their relevance. One marker, sCD27, was clinically validated in MS using two independent cohorts, for treatment response and prognosis.Conclusion Our splice variant and time-delay models substantially improved the prediction of protein abundance from mRNA data in three immune cell-types. The models provided valuable biomarker candidates, which were validated in clinical studies of MS and asthma. We propose that our strategy is generally applicable for biomarker discovery.
    • Three-Dimensional Electromagnetic Void Space

      Xu, Changqing; Chu, Hongchen; Luo, Jie; Hang, Zhi Hong; Wu, Ying; Lai, Yun (Physical Review Letters, American Physical Society (APS), 2021-09-17) [Article]
      Electromagnetic void space is a medium, while geometrically occupying a finite volume of space, optically equivalent to an infinitesimal point, in which electromagnetic waves do not experience any phase accumulation. Here, we report the first realization of three-dimensional (3D) electromagnetic void space by an all-dielectric photonic crystal possessing vanishing permittivity and permeability simultaneously. The 3D electromagnetic void space offers distinctive functionalities inaccessible to its 2D or acoustic counterparts because of the fundamental changes in topology, which comes from the ascension of dimensionality as well as the transverse nature of electromagnetic waves. In particular, we demonstrate, both theoretically and experimentally, that the transmission through such a 3D void space is unaffected by its inner boundaries, but highly sensitive to the outer boundaries. This enables many applications such as the impurity “antidoping” effect, outer-boundary-controlled switching, and 3D perfect wave steering. Our work paves a road toward 3D exotic optics of an optically infinitesimal point.
    • Shear wave velocity structure beneath Northeast China from joint inversion of receiver functions and Rayleigh wave group velocities: Implications for intraplate volcanism

      Tang, Zheng; Julià, Jordi; Mai, Paul Martin; Mooney, Walter; Wu, Yanqiang (Wiley, 2021-09-17) [Preprint]
      A high-resolution 3-D crustal and upper-mantle shear-wave velocity model of Northeast China is established by joint inversion of receiver functions and Rayleigh wave group velocities. The teleseismic data for obtaining receiver functions are collected from 107 CEA permanent sites and 118 NECESSArray portable stations. Rayleigh wave dispersion measurements are extracted from an independent tomographic study. Our model exhibits unprecedented detail in S-velocity structure. Particularly, we discover a low S-velocity belt at 7.5-12.5 km depth covering entire Northeast China (except the Songliao basin), which is attributed to a combination of anomalous temperature, partial melts and fluid-filled faults related to Cenozoic volcanism. Localized crustal fast S-velocity anomaly under the Songliao basin is imaged and interpreted as late-Mesozoic mafic intrusions. In the upper mantle, our model confirms the presence of low velocity zones below the Changbai mountains and Lesser Xing’an mountain range, which agree with models invoking sub-lithospheric mantle upwellings. We observe a positive S-velocity anomaly at 50-90 km depth under the Songliao basin, which may represent a depleted and more refractory lithosphere inducing the absence of Cenozoic volcanism. Additionally, the average lithosphere-asthenosphere boundary depth increases from 50-70 km under the Changbai mountains to 100 km below the Songliao basin, and exceeds 125 km beneath the Greater Xing’an mountain range in the west. Furthermore, compared with other Precambrian lithospheres, Northeast China likely has a rather warm crust (~480-970 °C) and a slightly warm uppermost mantle (~1200 °C), probably associated with active volcanism. The Songliao basin possesses a moderately warm uppermost mantle (~1080 °C).
    • Maximum principle preserving space and time flux limiting for Diagonally Implicit Runge-Kutta discretizations of scalar convection-diffusion equations

      Quezada de Luna, Manuel; Ketcheson, David I. (arXiv, 2021-09-17) [Preprint]
      We provide a framework for high-order discretizations of nonlinear scalar convection-diffusion equations that satisfy a discrete maximum principle. The resulting schemes can have arbitrarily high order accuracy in time and space, and can be stable and maximum-principle-preserving (MPP) with no step size restriction. The schemes are based on a two-tiered limiting strategy, starting with a high-order limiter-based method that may have small oscillations or maximum-principle violations, followed by an additional limiting step that removes these violations while preserving high order accuracy. The desirable properties of the resulting schemes are demonstrated through several numerical examples.
    • Crystallization and Morphology of Triple Crystalline Polyethylene-b-poly(ethylene oxide)-b-poly(ε-caprolactone) PE-b-PEO-b-PCL Triblock Terpolymers

      Matxinandiarena, Eider; Múgica, Agurtzane; Zubitur, Manuela; Ladelta, Viko; Zapsas, Georgios; Cavallo, Dario; Hadjichristidis, Nikos; Müller, Alejandro J. (Polymers, MDPI AG, 2021-09-16) [Article]
      The morphology and crystallization behavior of two triblock terpolymers of polymethylene, equivalent to polyethylene (PE), poly (ethylene oxide) (PEO), and poly (ε-caprolactone) (PCL) are studied: PE227.1-b-PEO4615.1-b-PCL3210.4 (T1) and PE379.5-b-PEO348.8-b-PCL297.6 (T2) (superscripts give number average molecular weights in kg/mol and subscripts composition in wt %). The three blocks are potentially crystallizable, and the triple crystalline nature of the samples is investigated. Polyhomologation (C1 polymerization), ring-opening polymerization, and catalyst-switch strategies were combined to synthesize the triblock terpolymers. In addition, the corresponding PE-b-PEO diblock copolymers and PE homopolymers were also analyzed. The crystallization sequence of the blocks was determined via three independent but complementary techniques: differential scanning calorimetry (DSC), in situ SAXS/WAXS (small angle X-ray scattering/wide angle X-ray scattering), and polarized light optical microscopy (PLOM). The two terpolymers (T1 and T2) are weakly phase segregated in the melt according to SAXS. DSC and WAXS results demonstrate that in both triblock terpolymers the crystallization process starts with the PE block, continues with the PCL block, and ends with the PEO block. Hence triple crystalline materials are obtained. The crystallization of the PCL and the PEO block is coincident (i.e., it overlaps); however, WAXS and PLOM experiments can identify both transitions. In addition, PLOM shows a spherulitic morphology for the PE homopolymer and the T1 precursor diblock copolymer, while the other systems appear as non-spherulitic or microspherulitic at the last stage of the crystallization process. The complicated crystallization of tricrystalline triblock terpolymers can only be fully grasped when DSC, WAXS, and PLOM experiments are combined. This knowledge is fundamental to tailor the properties of these complex but fascinating materials.
    • Intuitive and Efficient Roof Modeling for Reconstruction and Synthesis

      Ren, Jing; Zhang, Biao; Wu, Bojian; Huang, Jianqiang; Fan, Lubin; Ovsjanikov, Maks; Wonka, Peter (arXiv, 2021-09-16) [Preprint]
      We propose a novel and flexible roof modeling approach that can be used for constructing planar 3D polygon roof meshes. Our method uses a graph structure to encode roof topology and enforces the roof validity by optimizing a simple but effective planarity metric we propose. This approach is significantly more efficient than using general purpose 3D modeling tools such as 3ds Max or SketchUp, and more powerful and expressive than specialized tools such as the straight skeleton. Our optimization-based formulation is also flexible and can accommodate different styles and user preferences for roof modeling. We showcase two applications. The first application is an interactive roof editing framework that can be used for roof design or roof reconstruction from aerial images. We highlight the efficiency and generality of our approach by constructing a mesh-image paired dataset consisting of 2539 roofs. Our second application is a generative model to synthesize new roof meshes from scratch. We use our novel dataset to combine machine learning and our roof optimization techniques, by using transformers and graph convolutional networks to model roof topology, and our roof optimization methods to enforce the planarity constraint.
    • Features of structure, magnetic state and electrodynamic performance of SrFe12−xInxO19

      Turchenko, V A; Trukhanov, S V; Kostishin, V G; Damay, F; Porcher, F; Klygach, D S; Vakhitov, M G; Lyakhov, Dmitry; Michels, Dominik L.; Bozzo, B; Fina, I; Almessiere, M A; Slimani, Y; Baykal, A; Zhou, D; Trukhanov, A V (Scientific reports, Springer Science and Business Media LLC, 2021-09-16) [Article]
      Indium-substituted strontium hexaferrites were prepared by the conventional solid-phase reaction method. Neutron diffraction patterns were obtained at room temperature and analyzed using the Rietveld methods. A linear dependence of the unit cell parameters is found. In3+ cations are located mainly in octahedral positions of 4fVI and 12 k. The average crystallite size varies within 0.84–0.65 μm. With increasing substitution, the TC Curie temperature decreases monotonically down to ~ 520 K. ZFC and FC measurements showed a frustrated state. Upon substitution, the average and maximum sizes of ferrimagnetic clusters change in the opposite direction. The Mr remanent magnetization decreases down to ~ 20.2 emu/g at room temperature. The Ms spontaneous magnetization and the keff effective magnetocrystalline anisotropy constant are determined. With increasing substitution, the maximum of the ε/ real part of permittivity decreases in magnitude from ~ 3.3 to ~ 1.9 and shifts towards low frequencies from ~ 45.5 GHz to ~ 37.4 GHz. The maximum of the tg(α) dielectric loss tangent decreases from ~ 1.0 to ~ 0.7 and shifts towards low frequencies from ~ 40.6 GHz to ~ 37.3 GHz. The low-frequency maximum of the μ/ real part of permeability decreases from ~ 1.8 to ~ 0.9 and slightly shifts towards high frequencies up to ~ 34.7 GHz. The maximum of the tg(δ) magnetic loss tangent decreases from ~ 0.7 to ~ 0.5 and shifts slightly towards low frequencies from ~ 40.5 GHz to ~ 37.7 GHz. The discussion of microwave properties is based on the saturation magnetization, natural ferromagnetic resonance and dielectric polarization types.
    • Neural Étendue Expander for Ultra-Wide-Angle High-Fidelity Holographic Display

      Baek, Seung-Hwan; Tseng, Ethan; Maimone, Andrew; Matsuda, Nathan; Kuo, Grace; Fu, Qiang; Heidrich, Wolfgang; Lanman, Douglas; Heide, Felix (arXiv, 2021-09-16) [Preprint]
      Holographic displays can generate light fields by dynamically modulating the wavefront of a coherent beam of light using a spatial light modulator, promising rich virtual and augmented reality applications. However, the limited spatial resolution of existing dynamic spatial light modulators imposes a tight bound on the diffraction angle. As a result, today’s holographic displays possess low etendue, which is the product of the display area and the ´maximum solid angle of diffracted light. The low etendue forces a sacrifice of either the field ´ of view (FOV) or the display size. In this work, we lift this limitation by presenting neural etendue expanders. This new breed of optical elements, which is learned from a natural im- ´ age dataset, enables higher diffraction angles for ultra-wide FOV while maintaining both a compact form factor and the fidelity of displayed contents to human viewers. With neural etendue expanders, we achieve 64 ´ × etendue expansion of natural images with reconstruction ´ quality (measured in PSNR) over 29 dB on simulated retinal-resolution images. As a result, the proposed approach with expansion factor 64× enables high-fidelity ultra-wide-angle holographic projection of natural images using an 8K-pixel SLM, resulting in a 18.5 mm eyebox size and 2.18 steradians FOV, covering 85% of the human stereo FOV.
    • Low-Defect, High Molecular Weight Indacenodithiophene (IDT) Polymers Via a C–H Activation: Evaluation of a Simpler and Greener Approach to Organic Electronic Materials

      Ponder, James F.; Chen, Hung-Yang; Luci, Alexander M. T.; Moro, Stefania; Turano, Marco; Hobson, Archie L.; Collier, Graham S.; Perdigão, Luís M. A.; Moser, Maximilian; Zhang, Weimin; Costantini, Giovanni; Reynolds, John R.; McCulloch, Iain (ACS Materials Letters, American Chemical Society (ACS), 2021-09-16) [Article]
      The development, optimization, and assessment of new methods for the preparation of conjugated materials is key to the continued progress of organic electronics. Direct C–H activation methods have emerged and developed over the last 10 years to become an invaluable synthetic tool for the preparation of conjugated polymers for both redox-active and solid-state applications. Here, we evaluate direct (hetero)arylation polymerization (DHAP) methods for the synthesis of indaceno[1,2-b:5,6-b′]dithiophene-based polymers. We demonstrate, using a range of techniques, including direct visualization of individual polymer chains via high-resolution scanning tunneling microscopy, that DHAP can produce polymers with a high degree of regularity and purity that subsequently perform in organic thin-film transistors comparably to those made by other cross-coupling polymerizations that require increased synthetic complexity. Ultimately, this work results in an improved atom economy by reducing the number of synthetic steps to access high-performance molecular and polymeric materials.
    • Malat-1-PRC2-EZH1 interaction supports adaptive oxidative stress dependent epigenome remodeling in skeletal myotubes

      El Said, Nadine H.; Della Valle, Francesco; Liu, Peng; Paytuví-Gallart, Andreu; Adroub, Sabir; Gimenez, Juliette; Orlando, Valerio (Cell Death & Disease, Springer Science and Business Media LLC, 2021-09-16) [Article]
      AbstractPRC2-mediated epigenetic function involves the interaction with long non-coding RNAs (lncRNAs). Although the identity of some of these RNAs has been elucidated in the context of developmental programs, their counterparts in postmitotic adult tissue homeostasis remain uncharacterized. To this aim, we used terminally differentiated postmitotic skeletal muscle cells in which oxidative stress induces the dynamic activation of PRC2-Ezh1 through Embryonic Ectoderm Develpment (EED) shuttling to the nucleus. We identify lncRNA Malat-1 as a necessary partner for PRC2-Ezh1-dependent response to oxidative stress. We show that in this pathway, PRC2-EZH1 dynamic assembly, and in turn stress induced skeletal muscle targeted genes repression, depends specifically on Malat-1. Our study reports about PRC2–RNA interactions in the physiological context of adaptive oxidative stress response and identifies the first lncRNA involved in PRC2-Ezh1 function.
    • Evaluation of Thermoacoustic Applications Using Waste Heat to Reduce Carbon Footprint

      Spoor, Philip; Prabhudharwadkar, Deoras Mukund; Somu, Srinath; Saxena, Saumitra; Lacoste, Deanna; Roberts, William L. (American Society of Mechanical Engineers, 2021-09-16) [Conference Paper]
      Abstract Thermoacoustics (TA) engines and refrigerators typically run on the Stirling cycle with acoustic networks and resonators replacing the physical pistons. Without moving parts, these TA machines achieve a reasonable fraction of Carnot’s efficiency. They are also scalable, from fractions of a Watt up to kW of cooling. Despite their apparent promise, TA devices are not in widespread use, because outside of a few niche applications, their advantages are not quite compelling enough to dislodge established technology. In the present study, the authors have evaluated a selected group of applications that appear suitable for utilization of industrial waste heat using TA devices and have arrived at a ranked order. The principal thought is to appraise whether thermoacoustics can be a viable path, from both an economic and energy standpoint, for carbon mitigation in those applications. The applications considered include cryogenic carbon capture for power plant exhaust gases, waste-heat powered air conditioning/water chilling for factories and office buildings, hydrogen liquefaction, and zero-boiloff liquid hydrogen (LH2) storage. Although the criteria used for evaluating the applications are somewhat subjective, the overall approach has been consistent, with the same set of criteria applied to each of them. Thermoeconomic analysis is performed to evaluate the system viability, together with overall consideration of a thermoacoustic device’s general nature, advantages, and limitations. Our study convincingly demonstrates that the most promising application is zero-boiloff liquid hydrogen storage, which is physically well-suited to thermoacoustic refrigeration and requires cooling at a temperature and magnitude not ideal for standard refrigeration methods. Waste-heat powered air conditioning ranks next in its potential to be a viable commercial application. The rest of the applications have been found to have relatively lower potentials to enter the existing commercial space.
    • Minimizing Depth of Decision Trees with Hypotheses

      Azad, Mohammad; Chikalov, Igor; Hussain, Shahid; Moshkov, Mikhail (Springer International Publishing, 2021-09-16) [Conference Paper]
      In this paper, we consider decision trees that use both conventional queries based on one attribute each and queries based on hypotheses about values of all attributes. Such decision trees are similar to ones studied in exact learning, where membership and equivalence queries are allowed. We present dynamic programming algorithms for minimization of the depth of above decision trees and discuss results of computer experiments on various data sets and randomly generated Boolean functions.
    • Investigation of a Separated Short-Wavelength Peak in InGaN Red Light-Emitting Diodes

      Kirilenko, Pavel; Zhuang, Zhe; Iida, Daisuke; Velazquez-Rizo, Martin; Ohkawa, Kazuhiro (Crystals, MDPI AG, 2021-09-15) [Article]
      We fabricated indium gallium nitride (InGaN) red light-emitting diodes (LEDs) with a peak emission wavelength of 649 nm and investigated their electroluminescence (EL) properties. An additional separated peak in the EL spectrum of the red LEDs at 20 mA was observed at 465 nm. This additional peak also exhibits a blue-shift with increasing currents as does the main emission peak. Using high-resolution microscopy, we observed many point-like emission spots in the EL emission images at the currents below 1 mA. However, these emission spots cannot be identified at currents above 5 mA because the red emission from quantum wells (QWs) is much stronger than that emitted by these spots. Finally, we demonstrate that these emission spots are related to the defects generated in red QWs. The measured In content was lower at the vicinity of the defects, which was regarded as the reason for separated short-wavelength emission in red InGaN LEDs.
    • Capturing 3D atomic defects and phonon localization at the 2D heterostructure interface

      Tian, Xuezeng; Yan, Xingxu; Varnavides, Georgios; Yuan, Yakun; Kim, Dennis S.; Ciccarino, Christopher J.; Anikeeva, Polina; Li, Ming-yang; Li, Lain-Jong; Narang, Prineha; Pan, Xiaoqing; Miao, Jianwei (Science Advances, American Association for the Advancement of Science (AAAS), 2021-09-15) [Article]
      The three-dimensional (3D) local atomic structures and crystal defects at the interfaces of heterostructures control their electronic, magnetic, optical, catalytic, and topological quantum properties but have thus far eluded any direct experimental determination. Here, we use atomic electron tomography to determine the 3D local atomic positions at the interface of a MoS2-WSe2 heterojunction with picometer precision and correlate 3D atomic defects with localized vibrational properties at the epitaxial interface. We observe point defects, bond distortion, and atomic-scale ripples and measure the full 3D strain tensor at the heterointerface. By using the experimental 3D atomic coordinates as direct input to first-principles calculations, we reveal new phonon modes localized at the interface, which are corroborated by spatially resolved electron energy-loss spectroscopy. We expect that this work will pave the way for correlating structure-property relationships of a wide range of heterostructure interfaces at the single-atom level.
    • Two-Dimensional TiO2/TiS2 Hybrid Nanosheet Anodes for High-Rate Sodium-Ion Batteries

      Bayhan, Zahra; Huang, Gang; Yin, Jian; Xu, Xiangming; Lei, Yongjiu; Liu, Zhixiong; Alshareef, Husam N. (ACS Applied Energy Materials, American Chemical Society (ACS), 2021-09-15) [Article]
      The sodium-ion battery (NIB) is promising for next-generation energy storage systems. One promising anode material is titanium dioxide (TiO2). However, the sluggish sodiation/desodiation kinetics of TiO2 hinders its application in NIBs. Herein, we converted TiO2 into a two-dimensional (2D) TiO2/TiS2 hybrid to improve its sodium storage capability. The 2D TiO2/TiS2 hybrid nanosheet electrode provides high kinetics and excellent cycling performance for sodium-ion storage. This work provides a promising strategy to develop 2D hybrid nanomaterials for high-performance sodium storage devices.
    • High Throughput Printing of Two-Dimensional Materials into Wafer-scale Three-dimensional Architectures

      Wei, Xuan; Lin, Chia-Ching; Wu, Christine; Lu, Ang-Yu; Qaiser, Nadeem; Cai, Yichen; Fu, Jui-Han; Chiang, Yu-Hsiang; ding, lianhui; Ali, Ola; Xu, Wei; Zhang, Wenli; Kong, Jing; Chen, Han-Yi; Tung, Vincent (Research Square Platform LLC, 2021-09-15) [Preprint]
      Architected materials that actively respond to external stimuli hold tantalizing prospects for applications in energy storage, harvesting, wearable electronics and bioengineering. Transition metal dichalcogenides (TMDs) which represent the three-atom-thick, two-dimensional (2D) building blocks, are excellent candidates but have found limited success compared to metallic, inorganic, and organic counterparts due to the lack of up-scalable manufacturing. Here we report the high-throughput printing of 2D TMDs into wafer-scale 3D architectures with structural hierarchy across seven orders of magnitude between critical feature sizes. Anode made of 3D MoS2 architectures comprises the concentric vortex-like intricacy that unites technological merits from architecture, mechanical engineering, and electrochemistry not found in its bulk or exfoliated/epitaxy counterparts. The result is, contrary to expectation, the high-rate, high-capacity, and high-loading lithium (Li)-storage, surpassing those state-of-the-art anode designs while the technique offers an evaporation-like simplicity for industrial scalability.
    • Janus monolayers of magnetic transition metal dichalcogenides as an all-in-one platform for spin-orbit torque

      Smaili, Idris; Laref, Slimane; Garcia, Jose H.; Schwingenschlögl, Udo; Roche, Stephan; Manchon, Aurelien (Physical Review B, American Physical Society (APS), 2021-09-15) [Article]
      We theoretically predict that vanadium-based Janus dichalcogenide monolayers constitute an ideal platform for spin-orbit torque memories. Using first-principles calculations, we demonstrate that magnetic exchange and magnetic anisotropy energies are higher for heavier chalcogen atoms, while the broken inversion symmetry in the Janus form leads to the emergence of Rashba-like spin-orbit coupling. The spin-orbit torque efficiency is evaluated using optimized quantum transport methodology and found to be comparable to heavy nonmagnetic metals. The coexistence of magnetism and spin-orbit coupling in such materials with tunable Fermi-level opens new possibilities for monitoring magnetization dynamics in the perspective of nonvolatile magnetic random access memories.
    • Fracture Permeability Estimation Under Complex Physics: A Data-Driven Model Using Machine Learning

      He, Xupeng; Zhu, Weiwei; Santoso, Ryan; Alsinan, Marwa; Kwak, Hyung; Hoteit, Hussein (SPE, 2021-09-15) [Conference Paper]
      Abstract The permeability of fractures, including natural and hydraulic, are essential parameters for the modeling of fluid flow in conventional and unconventional fractured reservoirs. However, traditional analytical cubic law (CL-based) models used to estimate fracture permeability show unsatisfactory performance when dealing with different dynamic complexities of fractures. This work presents a data-driven, physics-included model based on machine learning as an alternative to traditional methods. The workflow for the development of the data-driven model includes four steps. Step 1: Identify uncertain parameters and perform Latin Hypercube Sampling (LHS). We first identify the uncertain parameters which affect the fracture permeability. We then generate training samples using LHS. Step 2: Perform training simulations and collect inputs and outputs. In this step, high-resolution simulations with parallel computing for the Navier-Stokes equations (NSEs) are run for each of the training samples. We then collect the inputs and outputs from the simulations. Step 3: Construct an optimized data-driven surrogate model. A data-driven model based on machine learning is then built to model the nonlinear mapping between the inputs and outputs collected from Step 2. Herein, Artificial Neural Network (ANN) coupling with Bayesian optimization algorithm is implemented to obtain the optimized surrogate model. Step 4: Validate the proposed data-driven model. In this step, we conduct blind validation on the proposed model with high-fidelity simulations. We further test the developed surrogate model with newly generated fracture cases with a broad range of roughness and tortuosity under different Reynolds numbers. We then compare its performance to the reference NSEs solutions. Results show that the developed data-driven model delivers good accuracy exceeding 90% for all training, validation, and test samples. This work introduces an integrated workflow for developing a data-driven, physics-included model using machine learning to estimate fracture permeability under complex physics (e.g., inertial effect). To our knowledge, this technique is introduced for the first time for the upscaling of rock fractures. The proposed model offers an efficient and accurate alternative to the traditional upscaling methods that can be readily implemented in reservoir characterization and modeling workflows.