Matrix Geometry Research Articles

A force-density framework for flexible multi-body dynamic analysis of clustered tensegrity structures

This paper develops a versatile and effective force-density framework for the flexible multi-body dynamic analysis of clustered tensegrity structures. In this framework, the force density is selected as the basic variable instead of force, and the clustered tensegrity structure is mathematically described in a vector and matrix form, encompassing topology, geometry, material, and force properties. A non-negative variable is defined as an indicator of the member stress state, and a complementary function is constructed to address the discontinuity issues that arise from the unidirectional axial stiffness of cables. Dynamic formulas are established within this force-density framework, with nodal coordinates selected as generalized parameters and formulations constructed in a matrix form. A complementary framework is established as an alternative for solving the dynamic equations, transforming the isolated steps of Newton’s iteration and cable state judgment (slack or tension) into a unified one, bringing more potential for improving solving efficiency. Numerical simulations are carried out to validate the approach, demonstrating that it effectively reveals the dynamic oscillation, tension changes, and cable slack behavior of clustered tensegrity structures during shape control. Comparative studies highlight the advantage of computational efficiency. The method proposed in this paper provides a robust mathematical model for studying clustered tensegrity structures, particularly regarding the shape control of deployable, active, and intelligent structures, aiding in understanding dynamic oscillation, tension changes, and cable slack behavior during their deformation. The methods can also be applied to cable net structures and other prestressed pin-jointed systems.

Thermophysical and transport properties of a pyrrolidinium-based ionic liquid confined in silica

Ionic liquid (IL) 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPyrrTFSI) was confined in silica (Aerosil A380) by direct mixing. The resulting BMPyrrTFSI/xSiO2 ionogel (x – from 2.3 to 6.7 wt%) was studied by TG, DSC, conductometry and viscometric methods. For confined IL, a decrease in the Tm and Ts-s by 14–16 °C and an increase in the Tg, and Tcc by 4–5 °C were found. With an increase in xSiO2, the opposite dynamics of the decomposition temperatures Tonset and Tpeak, and a disproportionate decrease in ionic conductivity were observed. The change in the properties of BMPyrrTFSI under conditions of limited geometry of the silica matrix is explained in the terms by the interaction of the IL and SiO2, as well as the conformation features of the cation and anion. In the first time, parameters such as the fragility index D and the formation factor F were also discussed for such systems. As a result, BMPyrrTFSI/4.5 wt% SiO2 ionogel (0.2 S m−1, 20 °C) was proposed as a promising electrolyte for application in electrochemical devices. This study may be useful for creating quasi-solid electrolytes based on ILs and inorganic materials.

A heat mining strategy for the potential Enhanced Geothermal System of the Acoculco Caldera Complex, Puebla (Mexico): A numerical approach based on Multiple Interacting Continua

As the world faces a transition to low-carbon electricity, energy markets have witnessed a fast expansion of Variable Renewable Energy, such as solar and wind power. In contrast, the installed capacity of geothermal electricity has increased with at a much lower rate. Continuous innovation is required to maintain geothermal electricity as a cost-competitive technology that helps building flexible power generation systems. Here we propose a heat mining setup for the promissory Enhanced Geothermal System (EGS) of the Acoculco caldera complex, which hosts a heat source in low permeability rocks. The conceptual model of the EGS reservoir consists of a fractured-porous layer between impermeable confining beds. An injection-production triplet is located in line with a fault plane that intersects the model area. Under the assumption of hydraulic stimulation to the fault zone, flow of the injection-production system restricts to a fracture network with secondary and variable permeability. Mass and heat transport is modeled following the Multiple Interacting Continua method with the software TOUGH2. We evaluate the performance of the heat mining system considering water and CO2 as working fluids for a given flow rate. We also evaluate the impact of fracture spacing in the reservoir performance. Results show that for a reservoir temperature of 300 °C, the CO2-based system experiences considerable adverse flow conditions that demands a higher pressure differential between the producer and injector (about 60 bar higher than the water-based reservoir). Likewise, the low heat capacity of CO2 imply a considerable limitation for heat mining. While for the water-based reservoir the cooling front extends throughout the entire reservoir at 30 yr of operation, for CO2 this happens in only about 60%. Additionally, the energy extracted per unit time in the water-based reservoir results more than twice the energy extracted with CO2. Finally, our numerical results show that fracture spacings in the range of 10 to 75 m behave similarly in terms of heat mining performance; decreasing the heat exchange area by increasing the fracture spacing from 10 to 75 m produces a minor impact under the assumption of high permeability fractures. Additional constrains for the fracture network, such as geometry, effective porosity and permeability of both fractures and rock matrix, have to be investigated in future research to better understand the possible performance of the production system.

Efficiency enhancement techniques in finite element analysis: navigating complexity for agile design exploration

PurposeThis paper aims to comprehensively explore techniques for reducing solution time in finite element analysis (FEA), addressing the critical need for expediting computations to facilitate agile design exploration within project timelines.Design/methodology/approachDrawing from a wide array of literature sources, this paper synthesizes and analyzes various methodologies used to enhance the efficiency of FEA. Techniques are scrutinized in terms of their applicability, effectiveness and potential limitations.FindingsThe review signifies application of linear assumptions across multiple facets of analysis and delves into matrix order reduction strategies, geometry simplification, symmetry exploitation, submodeling and mesh attribute control. It reveals how these techniques can effectively reduce computational burdens while maintaining acceptable levels of accuracy.Research limitations/implicationsWhile this review provides a comprehensive overview of existing efficiency enhancement techniques in FEA, it acknowledges inherent limitations of any synthesis-based study. Future research should focus on refining these methodologies.Practical implicationsThe insights provided in this paper offer practical guidance for structural engineers and researchers seeking to optimize FEA workflows. By implementing these techniques, practitioners can expedite solution times and enhance their ability to explore design alternatives efficiently ultimately leading to cost savings and more robust structures.Originality/valueThis review contributes to the existing literature by offering a comprehensive synthesis of efficiency enhancement techniques in FEA. By highlighting the originality and value of each discussed methodology, this paper provides a roadmap for future research and practical implementation in the field of structural engineering.

Random finite noncommutative geometries and topological recursion

In this paper, we investigate a model for quantum gravity on finite noncommutative spaces using the theory of blobbed topological recursion. The model is based on a particular class of random finite real spectral triples {(\mathcal{A}, \mathcal{H}, D, \gamma, J)} , called random matrix geometries of type {(1,0)} , with a fixed fermion space {(\mathcal{A}, \mathcal{H}, \gamma, J)} and a distribution of the form {e^{- \mathcal{S} (D)}\, {\mathrm{d}} D} over the moduli space of Dirac operators. The action functional {\mathcal{S} (D)} is considered to be a sum of terms of the form {\prod_{i=1}^s \mathrm{Tr} ({D^{n_i}})} for arbitrary {s \geqslant 1} . The Schwinger–Dyson equations satisfied by the connected correlators {W_n} of the corresponding multi-trace formal 1-Hermitian matrix model are derived by a differential geometric approach. It is shown that the coefficients {W_{g,n}} of the large N expansion of {W_n} ’s enumerate discrete surfaces, called stuffed maps, whose building blocks are of particular topologies. The spectral curve {( {\Sigma, \omega_{0,1}, \omega_{0,2}} )} of the model is investigated in detail. In particular, we derive an explicit expression for the fundamental symmetric bidifferential {\omega_{0,2}} in terms of the formal parameters of the model.

Modified plastic damage model for steel fiber reinforced concrete

AbstractSteel fiber reinforced concrete (SFRC) structures have been widely adopted and attracted great research attention due to their excellent performance in resisting tension and flexure bending. However, the existing analytical and numerical analyses of SFRC structures rely mainly on the experimental data of material tests, thereby being suitable for a case‐by‐case basis. This is due to the lack of a general and reliable constitutive material model for SFRC, which analytically considers the fiber‐dependent parameters such as fiber geometry, fiber stiffness, and interface properties of fibers and concrete matrix. This study presents an approach to modify the concrete plastic damage model to represent the SFRC material constitutive relations for simulating the structural behavior of SFRC. In this approach, the general procedure to integrate the bridging effect of fibers through the pull‐out mechanism into the constitutive relation of SFRC was proposed. The comparison between the numerical and experimental results was conducted to verify the reliability of the proposed model. The results demonstrated the proposed model could well represent the material performance of SFRC and the numerical simulations could capture reasonably the effect of the volume fraction, geometry, and properties of fibers on the structural response of SFRC.

Oxidation, reduction and semi-classical limit for quantum matrix geometries

Matrix configurations define noncommutative spaces endowed with extra structure including a generalized Laplace operator, and hence a metric structure. Made dynamical via matrix models, they describe rich physical systems including noncommutative gauge theory and emergent gravity. Refining the construction in [25], we construct a semi-classical limit through an immersed submanifold of complex projective space based on quasi-coherent states. We observe the phenomenon of oxidation, where the resulting semi-classical space acquires spurious extra dimensions. We propose to remove this artifact by passing to a leaf of a carefully chosen foliation, which allows to extract the geometrical content of the noncommutative spaces. This is demonstrated numerically via multiple examples.

NUMERICAL DESIGN OF ASYMMETRIC POROUS MATERIALS WITH TARGET PROPERTIES

Numerical tools have become ubiquitous in design of manufactured porous materials. Many methods have been developed for imaging, reconstruction, material property estimation, and generation of materials in a virtual environment with the ultimate goal of understanding the connection between the synthesis process, material microstructure, and material properties. In previous works, we presented a new random field-based generation technique called adjustable level cut filtered Poisson field (ALCPF). We paired the ALCPF technique with a flow simulation method, the pore topology method (PTM), to compute material properties and verify that targets have been attained. Building on our earlier work where we demonstrated the ability of ALCPF to efficiently generate a wide variety of homogeneous microstructures, we pursue three new goals. First, we extend ALCPF to produce heterogeneous asymmetric porous materials with a target pore size gradient. Second, we demonstrate the capability of asymmetric-ALCPF to control both solid and void spaces by generating virtual asymmetric materials with different types of solid matrix geometries and void space pore size gradients. Third, we use these materials to assess the accuracy of PTM results in comparison with the solution from a direct numerical simulation. This work demonstrates that the ALCPF method successfully generates porous microstructures with desired asymmetric geometry with less than 4% error compared to target pore size gradient. Also, PTM estimates permeability with an average error of less than 7% compared to direct numerical simulation results.

Integrated Cross-Scale Manipulation and Modulable Encapsulation of Cell-Laden Hydrogel for Constructing Tissue-Mimicking Microstructures.

Engineered microstructures that mimic invivo tissues have demonstrated great potential for applications in regenerative medicine, drug screening, and cell behavior exploration. However, current methods for engineering microstructures that mimic the multi-extracellular matrix and multicellular features of natural tissues to realize tissue-mimicking microstructures invitro remain insufficient. Here, we propose a versatile method for constructing tissue-mimicking heterogeneous microstructures by orderly integration of macroscopic hydrogel exchange, microscopic cell manipulation, and encapsulation modulation. First, various cell-laden hydrogel droplets are manipulated at the millimeter scale using electrowetting on dielectric to achieve efficient hydrogel exchange. Second, the cells are manipulated at the micrometer scale using dielectrophoresis to adjust their density and arrangement within the hydrogel droplets. Third, the photopolymerization of these hydrogel droplets is triggered in designated regions by dynamically modulating the shape and position of the excitation ultraviolet beam. Thus, heterogeneous microstructures with different extracellular matrix geometries and components were constructed, including specific cell densities and patterns. The resulting heterogeneous microstructure supported long-term culture of hepatocytes and fibroblasts with high cell viability (over 90%). Moreover, the density and distribution of the 2 cell types had significant effects on the cell proliferation and urea secretion. We propose that our method can lead to the construction of additional biomimetic heterogeneous microstructures with unprecedented potential for use in future tissue engineering applications.

Generating quantum matrix geometry from gauged quantum mechanics

Generating quantum matrix geometry from gauged quantum mechanics

Sample thickness affects contrast and measured shape in TEM images and in electron tomograms

We investigated the effect of nanoparticle (NP) image broadening and its contrast change dependence on a support matrix thickness in a transmission electron microscope (TEM). We measured the effect of NP size and atomic number on its image broadening. Based on the experimental TEM images we generated tomograms of NPs on four types of support matrix. The measured shape aspect ratio of the NPs in such tomograms depends on the geometry of the support matrix. For example, the aspect ratio of 6 nm NP placed on a thin film with window-frame support is 1.14, while the aspect ratio of 6 nm NP on a rod-shaped support with 910 nm diameter is 1.67 in a tomogram.

Large‐eddy simulation of a channel flow over an irregular porous matrix

AbstractFor turbulent flows in porous media, it is often assumed that the irregularity of the matrix would not affect the macroscopic, double‐averaged (in time and space), parameters of turbulence. Hence, to improve currently used modelling techniques, the ongoing efforts of the community are focused on performing high‐fidelity, scale‐resolving simulations of flows in regular, periodically repeating porous structures. This approach allows for minimizing still large computational cost, however, it assumes that results obtained from those geometries are generalizable to more disordered configurations. We investigate this assumption numerically using large‐eddy simulation and analyse the influence of the irregularity of the porous structure on turbulent characteristics in a fully turbulent flow in a channel half‐filled with porous medium. The flow statistics are examined and compared between four simulations, a reference channel with regular three‐dimensional porous matrix consisting of an array of cubes and three similar geometries created from randomly perturbing the positions of the cubes, with increasing mean value of cube displacement. We study double‐averaged flow properties, the distributions of double‐averaged Reynolds stress tensor, including the anisotropy of macroscopic turbulence and the drag force induced by the flow in the porous region of the channel. The results confirm the idea that the averaged characteristics, including the anisotropy of the stress tensor and the drag force, are not greatly influenced by the moderate perturbation to the geometry of the porous matrix. Additionally, the macroscopic turbulence seems to exhibit a high degree of anisotropy in the porous region and the adjacent boundary layer, suggesting that second‐order closure could be an adequate modelling choice for such flows.

Aerothermal characteristics past a matrix structure inside a rectangular serpentine passage

A matrix structure can offer a high heat transfer and improved structural rigidity to the gas turbine's aerofoils. The earlier matrix studies are limited to presenting aerothermal behavior within the matrix structures. Thus, there is a scope to investigate the aerothermal characteristics downstream of a matrix geometry. The present experimental effort seeks to characterize the detailed flow and heat transfer downstream of the matrix and at the bend for Re = 800 and 6500. The heat transfer and flow fields are captured in various planes using liquid crystal thermography and stereoscopic particle image velocimetry techniques. The results show that the matrix ejects a highly turbulent vortical flow in the form of two co-rotating vortices, which further diffuse and merge in downstream. The matrix offers a very high average augmentation (Nu¯/Nu¯0) in the first pass for Re = 800 (varies from 12 to 4), but it shows a poor heat transfer (Nu¯/Nu¯0 < 1) at the bend region, which can generate local hot spots for Re = 800. In contrast, for Re = 6500, the matrix offers a stable augmentation throughout the first pass and bend region, i.e., Nu¯/Nu¯0≈ 2.4–1.

Improving volume-averaged simulations of matrix-stabilized combustion through direct X-ray µCT characterization: Application to NH3/H2-air combustion

Porous media combustion (PMC) relies on internal heat recirculation in an open-cell ceramic foam matrix to enhance the flame speed of fuels with poor combustion properties. Volume-averaged simulations are often used to study the combustion performance and pollutant emissions of such systems. However, due to the varying complexity of matrix geometries found in practical burners, as well as the wide range of closure models for the constitutive relations of the solid phase, contradicting statements about the predictive accuracy of these volume-averaged models can be found in the literature. In this work, we propose an open-source modeling framework for accurate volume-averaged PMC simulations by using first-principles methods to determine effective properties used in closure models. This framework relies on adequately characterizing the topology of the solid matrix, using commonly available X-ray computed microtomography. With this approach, significant improvements in accuracy are reported compared to empirical models from the literature. The framework based on first-principle evaluations of constitutive relations is compared against experimental measurements conducted on an interface-stabilized burner operated with premixed NH3/H2-air. The model shows good agreement for exhaust gas composition and stability limits. The proposed simulation framework performs significantly better than state-of-the-art techniques that employ commonly used empirical correlations for effective matrix properties. Statement of SignificanceWe present a new open-source simulation framework for improved characterization of porous media combustion. By utilizing µCT techniques, accurate effective matrix properties can be determined from first-principle simulations. These effective properties are used in closure models for 1D volume-averaged reacting flow simulations using appropriate sub-models for heat recirculation. This modeling framework is able to reliably predict stability limits while conventional closure models yield erroneous trends. Assessment of the resulting modeling framework is performed using experiments with exhaust gas characterization performed on a NH3/H2-air porous media burner.

Surrogate modeling and global sensitivity analysis for the simultaneous growth of multiple hydraulic fractures

Hydraulic fracturing has been widely used in enhancing the conductivity of the rock formations and increasing the rate of extraction of unconventional resources. During hydraulic fracturing treatments, there are considerable uncertainties in the completion operations and measurement of the geomechanical parameters such as the perforation geometry and elastic modulus of the rock matrix, which may result in a large error in fracture pattern prediction and parameter optimization when deterministic models are implemented. Therefore, a good understanding of the impact of the input uncertainties on the output predictions, also referred to as uncertainty quantification, has become a major issue. In this paper, a non-intrusive stochastic model is developed by combining a fully coupled hydraulic fracturing model based on the dual boundary element method with a surrogate model using polynomial chaos expansion. The perforation geometry, mechanical parameters of the rock formation, orientation and magnitude of the in-situ stress are treated as random variables. The surrogate model is constructed using data from the hydraulic fracturing model and is capable of providing fast approximations of the objectives, thereby making Monte Carlo simulations and sensitivity studies feasible. The stochastic model is validated against the random responses predicted by semi-analytical solutions for the single fracture case and shows excellent agreements with a relative error less than 0.1% for the injection pressure and 1% for the maximum aperture. The impact of the geomechanical and geometric parameter randomness on the growth of multiple fractures is investigated. The results show that the randomness in the fracture toughness and Young’s modulus plays an important role in fracture growth among geomechanical parameters, and the uncertainty of the fracture pattern is mostly attributed to the randomness in the initial length and aperture of the inner fracture among geometric uncertainties.

Introduction to special issue on single cell analysis

Journal of Innovative Optical Health SciencesVol. 16, No. 02, 2302002 (2023) EditorialOpen AccessIntroduction to special issue on single cell analysisShuhua Yue, Xuantao Su, Minbiao Ji, Fu Wang, and Xunbin WeiShuhua YueSchool of Biological Science and Medical Engineering, Beihang University, 37 Xueyuan Road, Haidian District, Beijing 100191, ChinaE-mail Address: [email protected] Search for more papers by this author , Xuantao SuSchool of Microelectronics, Shandong University, 1500 Shunhua Road, Gaoxin District, Jinan 250101, ChinaE-mail Address: [email protected] Search for more papers by this author , Minbiao JiDepartment of Physics, Fudan University, 2005 Songhu Road, Yangpu District, Shanghai 200438, ChinaE-mail Address: [email protected] Search for more papers by this author , Fu WangSchool of Biomedical Engineering, Shanghai Jiao Tong University, 1954 Huashan Road, Xuhui District, Shanghai 200030, ChinaE-mail Address: [email protected] Search for more papers by this author , and Xunbin WeiDepartment of Biomedical Engineering, Peking University, 38 Xueyuan Road, Haidian District, Beijing 100191, ChinaE-mail Address: [email protected]Corresponding author. Search for more papers by this author https://doi.org/10.1142/S1793545823020029Cited by:0 Next This article is part of the issue: Special Issue on Single Cell AnalysisGuest Editors: Shuhua Yue, Xuantao Su, Minbiao Ji, Fu Wang and Xunbin Wei AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Librarian ShareShare onFacebookTwitterLinked InRedditEmail Increasing evidence has shown that cell populations are not homogeneous, but rather heterogeneous, even within very small cell populations. Bulk measurements based on the homogenized cell population do not account for the critical changes occurring in individual cells and are sometimes misleading. Cellular heterogeneity characteristics may be the key to address previously unsolved questions in disease development and progression. Therefore, it is crucial to develop novel single cell analysis techniques, including spectroscopy, imaging, sensing, manipulating, and sorting. This special issue, including three review articles and five original research articles, highlights recent progress in the development of single-cell optical analysis techniques and their applications in biological discovery, disease diagnosis, and treatment.A number of advanced optical imaging methods have been recently developed for single cell analysis. Stimulated Raman scattering (SRS) microscopy, an attractive imaging technique with advantages of high chemical selectivity, high spatial resolution, and high imaging speed, has become a powerful tool for biology and medicine. Jing Huang and Minbiao Ji reviewed the principles of SRS, discussed the technical developments and implementations of SRS microscopy, then highlighted and summarized its applications on biological cellular machinery, and finally shared visions of potential breakthroughs in the future.1 Light field microscopy (LFM) is an elegant non-scanning imaging tool to achieve real-time three-dimensional (3D) volumetric imaging of single cells with a single shot. Beibei Gao et al. reviewed the principle and development of LFM, discussed the improved approaches based on hardware designs and 3D reconstruction algorithms, and presented the applications in single-cell imaging.2 As an emerging single-cell imaging modality, microwave-induced thermoacoustic imaging (MTAI), with the assistance of functional nanoparticles, has shown broad prospects in biomedical and clinical applications. Xiaoyu Tang et al. reviewed the recent progress, challenges, and future directions of MTAI integrated with functional nanoparticles.3 Besides imaging instrumentation, processing algorithm is also very important for single-cell analysis. Shutong Liu et al. proposed a new feature extraction method in fluorescence imaging of nucleus to achieve automatic and accurate identification of apoptosis with low cost in terms of time,4 which may facilitate large-scale single-cell analysis.The advanced single-cell optical methods have been increasingly applied for biological discovery and disease diagnosis. Exosome has been considered as a promising biomarker for diagnosis of early-stage cancer. Xiao Ma et al. achieved label-free breast cancer detection and classification by convolutional neural network-based exosomes surface-enhanced Raman scattering.5 Actin cytoskeleton plays crucial roles in various cellular functions. Fulin Xing et al. reported the regulation of actin cytoskeleton via photolithographic micropatterning, which provides new insights into how geometry of extracellular matrix (ECM) regulates the organization of actin cytoskeleton.6 Siyi Qiu et al. revealed microbial spore responses to microwave radiation by single-cell analysis, providing a new perspective on the responses of living single cells to microwave radiation.7 Fanyi Kong et al. showed continuous infrared light suppressed transmembrane Na currents irrelevant to K channel on the freshly isolated hippocampal neuron cell, which could be explained by a membrane capacitance mediation process.8Finally, we would like to thank all the contributing authors for making this issue possible. More articles focused on Single Cell Analysis will be published in the next special issue.

ИССЛЕДОВАНИЕ ПРОЦЕССА ФОРМООБРАЗОВАНИЯ ПОПЕРЕЧНОГО ГОФРА СИЛЬФОНА С МИНИМАЛЬНОЙ РАЗНОТОЛЩИННОСТЬЮ

In the article, studies were carried out to determine the possibility of confirming the hypothesis put forward about obtaining a more uniform bellows wall in the region of the corrugation top by shaping the bellows with an elastic medium in a two-stage method in a detachable sectional matrix using constrained bending technology. A description of the areas of application of bellows, their designs is given, the most advanced methods of manufacturing bellows and their main drawback are identified. The purpose of the study is defined and the corresponding tasks that need to be solved are set. The study used analytical research methods and finite element modeling. A method for shaping the bellows and the geometry of the shaping matrix are proposed. A technique for calculating the parameters of the technological process for two stages of bellows shaping is given. Pictures of the relative change in the thickness of the bellows corrugation during shaping in the traditional way and when shaping by the proposed method are presented. The distribution fields of equivalent stresses according to Mises are presented at the first and second transitions during shaping by the proposed method. A comparison is made and an assessment of the obtained results is given.

Motor Imagery EEG Classification Based on Riemannian Sparse Optimization and Dempster-Shafer Fusion of Multi-Time-Frequency Patterns.

Motor imagery-based brain-computer interfaces (MI-BCIs) features are generally extracted from a wide fixed frequency band and time window of EEG signal. The performance suffers from individual differences in corresponding time to MI tasks. In order to solve the problem, in this study, we propose a novel method named Riemannian sparse optimization and Dempster-Shafer fusion of multi-time-frequency patterns (RSODSF) to enhance the decoding efficiency. First, we effectively combine the Riemannian geometry of the spatial covariance matrix with sparse optimization to extract more robust and distinct features. Second, the Dempster-Shafer theory is introduced and used to fuse each time window after sparse optimization of Riemannian features. Besides, the probabilistic values of the support vector machine (SVM) are obtained and transformed to effectively fuse multiple classifiers to leverage potential soft information of multiple trained SVM. The open-access BCI Competition IV dataset IIa and Competition III dataset IIIa are employed to evaluate the performance of the proposed RSODSF. It achieves higher average accuracy (89.7% and 96.8%) than state-of-the-art methods. The improvement over the common spatial patterns (SFBCSP) are respectively 9.9% and 12.4% (p < 0.01, paired t-test). These results show that our proposed RSODSF method is a promising candidate for the performance improvement of MI-BCI.

Polylactic Acid/Polyaniline Nanofibers Subjected to Pre- and Post-Electrospinning Plasma Treatments for Refined Scaffold-Based Nerve Tissue Engineering Applications

Composite biopolymer/conducting polymer scaffolds, such as polylactic acid (PLA)/ polyaniline (PAni) nanofibers, have emerged as popular alternative scaffolds in the electrical-sensitive nerve tissue engineering (TE). Although mimicking the extracellular matrix geometry, such scaffolds are highly hydrophobic and usually present an inhomogeneous morphology with massive beads that impede nerve cell-material interactions. Therefore, the present study launches an exclusive combinatorial strategy merging successive pre- and post-electrospinning plasma treatments to cope with these issues. Firstly, an atmospheric pressure plasma jet (APPJ) treatment was applied on PLA and PLA/PAni solutions prior to electrospinning, enhancing their viscosity and conductivity. These liquid property changes largely eliminated the beaded structures on the nanofibers, leading to uniform and nicely elongated fibers having average diameters between 170 and 230 nm. After electrospinning, the conceived scaffolds were subjected to a N2 dielectric barrier discharge (DBD) treatment, which significantly increased their surface wettability as illustrated by large decreases in water contact angles for values above 125° to values below 25°. X-ray photoelectron spectroscopy (XPS) analyses revealed that 3.3% of nitrogen was implanted on the nanofibers surface in the form of C-N and N-C=O functionalities upon DBD treatment. Finally, after seeding pheochromocytoma (PC-12) cells on the scaffolds, a greatly enhanced cell adhesion and a more dispersive cell distribution were detected on the DBD-treated samples. Interestingly, when the APPJ treatment was additionally performed, the extension of a high number of long neurites was spotted leading to the formation of a neuronal network between PC-12 cell clusters. In addition, the presence of conducting PAni in the scaffolds further promoted the behavior of PC-12 cells as illustrated by more than a 40% increase in the neurite density without any external electrical stimulation. As such, this work presents a new strategy combining different plasma-assisted biofabrication techniques of conducting nanofibers to create promising scaffolds for electrical-sensitive TE applications.

Analytical model for steady-state solute diffusion in non-isothermal fractured porous media

Mass transfer in non-isothermal fractured porous media have a wide application in many natural phenomena and engineering processes. The current study focuses on developing alternative formulations of steady-state analytical modelling for thermally induced solute diffusion in fractured porous media. The proposed analytical frameworks are validated by two set of experimental data. The varied examples of coupled heat transfer and solute diffusion are evaluated by the proposed solution to discuss the effects of thermal diffusion, flow operational conditions, geometry and thermal properties of fracture and matrix on the overall transport of solute in a fractured porous media. It is found that thermal-diffusion process, or explicitly as a “Soret effect (ST)”, is a non-negligible part for investigating solute transport in non-isothermal fractured porous media. For example, increasing ST from 10-3 K−1 to 10-2 K−1 leads to a reduction of solute concentration by a factor of 1.2. We demonstrate that a larger Peclet number ensures the temperature of the solute along the fracture decreasing while its concentration along the fracture increasing. However, an increase of the temperature difference between the entry and the output shows an opposite trend. An increase in fracture aperture or matrix thickness leads to temperature decreasing and concentration increasing along the fracture and matrix as a larger amount of solute are injected from the inlet boundary. The presented analytical solutions may also serve as a benchmark test tool for alternative numerical studies of coupled heat transfer and solute diffusion in fractured porous media.