Fiber Spacing Research Articles

Stratified Hilbert Modules on Bounded Symmetric Domains

We analyze the “eigenbundle” (localization bundle) of certain Hilbert modules over bounded symmetric domains of rank r, giving rise to complex-analytic fibre spaces which are stratified of length r+1. The fibres are described in terms of Kähler geometry as line bundle sections over flag manifolds, and the metric embedding is determined by taking derivatives of reproducing kernel functions. Important examples are the determinantal ideals defined by vanishing conditions along the various strata of the stratification.

Essential surfaces in Seifert fiber spaces with singular surfaces

Two-sided incompressible surfaces in Seifert fiber spaces with isolated singular fibers are well-understood. Frohman [3] and Rannard [6] have shown that one-sided incompressible surfaces in Seifert fiber spaces which have isolated singular fibers are either pseudo-horizontal or psuedo-vertical. We extend their result to characterise essential surfaces in Seifert fiber spaces which may have singular surfaces, i.e., in S1-foliated 3-manifolds which have fibered model neighbourhoods that are isomorphic to either a fibered solid torus or a fibered solid Klein bottle.

Stochastic RBFN-based reliability estimation of variable fiber spacing composite plates under thermal loading

Stochastic RBFN-based reliability estimation of variable fiber spacing composite plates under thermal loading

Effect of fabric structural stability on the tensile property of bidirectional angle-interlock woven composites

Three-dimensional bidirectional angle-interlock woven (3DBAW) composites exhibit the orthogonal high modulus, which has the potential to be used in load-bearing components. 3DBAW preforms prepared using the certain and uncertain cross-sectional yarns exhibit various structural characteristics, and the mechanical properties of composites show the high variation. To investigate the effect of fabric structural stability on the elastic properties of 3DBAW composites and broaden its application, contrast analysis of quasi-static tensile properties of composite specimens was proposed, and the failure mechanism was analysed. The results showed that the high tensile initial elastic modulus of 3DBAW composites was attributed to the low curvature of load-bearing yarns. For composites with stable fabrics, the tensile process was smooth and steady owing to the uniform fiber spacing, and the tensile elastic modulus and strength show the smaller coefficient of variation. The tensile crack surfaces of composites with stable structural fabrics were regular, and making the full use of the load-bearing yarns. 3DBAW preforms with stable structure can effectively reduce the fluctuation of changes at the initial stage of loading, and the translaminar fracture and adhesive matrix failure are the main failure modes without the obvious interlaminar fracture. The results provided the support for the application of 3DBAW composite in load-bearing components.

On the collapsing of Calabi–Yau manifolds and Kähler–Ricci flows

Abstract We study the collapsing of Calabi–Yau metrics and of Kähler–Ricci flows on fiber spaces where the base is smooth. We identify the collapsed Gromov–Hausdorff limit of the Kähler–Ricci flow when the divisorial part of the discriminant locus has simple normal crossings. In either setting, we also obtain an explicit bound for the real codimension-2 Hausdorff measure of the Cheeger–Colding singular set and identify a sufficient condition from birational geometry to understand the metric behavior of the limiting metric on the base.

A study of conformal Riemannian maps whose total manifold admits a Yamabe soliton

We study conformal Riemannian maps between Riemannian manifolds and derive expression of scalar curvature for its total manifold. Later, we study conformal Riemannian maps whose total manifold admits a Yamabe soliton and obtain conditions for fiber and range space of such maps to be Yamabe soliton. We also present a characterization theorem for a Yamabe soliton to be an almost Yamabe soliton for conformal Riemannian maps. Finally, we derive a nontrivial example of a conformal Riemannian map whose total manifold admits a Yamabe soliton.

3D Printing Process Research and Performance Tests on Sodium Alginate-Xanthan Gum-Hydroxyapatite Hybridcartilage Regenerative Scaffolds.

Cartilage injury is a common occurrence in the modern world. Compared with traditional treatment methods, bio-3D printing technology features better utility in the field of cartilage repair and regeneration, but still faces great challenges. For example, there is currently no means to generate blood vessels inside the scaffolds, and there remains the question of how to improve the biocompatibility of the generated scaffolds, all of which limit the application of bio-3D printing technology in this area. The main objective of this article was to prepare sodium alginate-xanthan gum-hydroxyapatite (SA-XG-HA) porous cartilage scaffolds that can naturally degrade in the human body and be used to promote cartilage damage repair by 3D printing technology. First, the viscosities of SA and XG were analyzed, and their optimal ratio was determined. Second, a mathematical model of the hybrid slurry was established based on the power-law fluid model, in which the printing pressure, needle movement speed, and fiber spacing were established as important parameters affecting the printing performance of the composite. Third, by performing a finite element simulation of the printing process and combining it with the actual printing process, suitable printing parameters were determined (air pressure of 1 bar, moving speed of 9 mm/s, line spacing of 1.6 mm, and adjacent layers of 0-90°). Fourth, composite scaffolds were prepared and tested for their compressive properties, degradation properties, cytotoxicity, and biocompatibility. The results showed that the novel composite scaffolds prepared in this study possessed good mechanical and biological properties. Young's modulus of the composite scaffolds reached 130 KPa and was able to maintain a low degradation rate in simulated body fluid solution for >1 month. The activity of the C5.18 chondrocytes in the scaffold leach solution exceeded 120%. The cells were also able to proliferate densely on the scaffold surface.

Effect of the polyacrylonitrile mass fraction on the structure of coaxial polyacrylonitrile/mesophase pitch composite fibers

AbstractTo minimize structural heterogeneity during graphitization of polyacrylonitrile (PAN)‐based carbon fibers, the present authors prepare coaxial composite fibers with PAN as the skin and a PAN/MP mixture as the core by wet spinning with coaxial spinning needles. With increasing PAN mass fraction in the skin‐layer solution, the crystallinity of the coaxial composite fibers increases from 24.3% to 31.4%, and the crystal plane spacing of the coaxial composite fibers decreases from 0.529 to 0.523 nm. The tensile strength of the coaxial composite fibers increases by 122%, attributable to the crystallinity increase from 24.3% at 10 wt% PAN to 31.4% at 15 wt% PAN. Scanning electron microscope images of the coaxial fibers demonstrate that the cortical region changes from a porous, loose structure to a less porous, denser structure. Gray value testing of the coaxial composite fibers shows that transition layers formed at the interface between the cortex and core layers, which was formed for the outward diffusion of the core‐layer MP and PAN mixed solution. With increasing PAN mass fraction, because of the high viscosity of the cortical PAN solution, diffusion of the core‐layer mixed solution to the cortical layer decreases, resulting in a 75.2% increase in the core area ratio of the coaxial composite fibers.

Time Coding-Based Single-Photon-Counting Lidar for Obtaining Spatial Location

This paper proposes a single-photon-counting lidar based on time coding that can obtain the target’s spatial location and measure the distance and azimuth angle in real time without needing a scanning device. Multiple optical fibers were used to introduce laser echo photons into a single-pixel single-photon detector. According to the deviation in the detection time of the echo photons passing through different optical fibers, multiple distances can be obtained simultaneously. Combining the measured distances with the fiber spacing allows the calculation of the distance, azimuth angle, and spatial coordinates of the target. This lidar has the advantages of high photon detection efficiency, short signal acquisition time, and low cost compared to array detectors.

Numerical statistics-based research on the spatial distribution of cylindrical fiber in ideal simulated fiber reinforced concrete matrix

The macro properties of fiber reinforced concrete is significantly associated with the spatial distribution of fiber. In this paper, the statistics-based algorithms characterizing fiber spatial distribution including orientation probability, spacing distance and wall effect were proposed based on the established the random generation model of cylindrical fibers in an ideal three-dimensional fiber reinforced concrete matrix. The influence of fiber physical parameters on the overall fiber spatial distribution were statistically analyzed. The results show that the fiber orientation probability in ideal fiber reinforced concrete matrix is almost constant. The fiber geometric size plays an important role on the fiber spatial morphological characteristics, where the fiber spacing distance increases with the fiber length and diameter, and the wall effect is significantly affected by the fiber length. The heterogeneity of fiber distribution characterized by the higher fiber spacing distance in the edge region is associated with the fiber sparsity mainly influenced by the single fiber volume and total fiber fraction. With the constraints of wall effect and principal stress direction, the boundary region parallel to the principal stress has a higher fiber orientation coefficient, while the region perpendicular to principle stress possesses of the lowest coefficient.

Near-perfect suppression of Li dendrite growth by novel porous hollow carbon fibers embedded with ZnO nanoparticles as stable and efficient anode for Li metal batteries

For the practical application of next-generation Li metal batteries (LMBs), a Li metal anode with high safety and efficiency is essential. However, LMBs still suffer from the problems caused by the growth of Li dendrites at the Li metal anode. In this study, we introduce a novel way that could dramatically suppress the growth of Li dendrites and improve the performance of LMBs. A free-standing porous hollow carbon nanofiber embedded with lithiophilic ZnO nanoparticles (P-HCNF@ZnO) is fabricated using a dual-nozzle electrospinning technique followed by carbonization. The nano-sized pores formed in the shell of hollow carbon fiber provide passages for Li ions to penetrate into the core space of the hollow fiber, and the lithiophilic ZnO particles play a decisive role in inducing and plating Li ions inside the core efficiently and uniformly. Therefore, Li ions are mostly electroplated/stripped on the internal surface of the porous hollow fibers and dendrites are rarely formed on their exterior surface even under fast lithiation conditions, while numerous Li dendrites are formed on the exterior surface of the non-porous hollow fiber electrode (HCNF@ZnO). As a result, the P-HCNF@ZnO electrode exhibits a very low over-potential of about 87 mV, a stable capacity retention of about 95% at a high current density of 1.0 mA cm−2, and a much higher performance than HCNF@ZnO in a symmetric cell test. Furthermore, in full cell tests, the LiFePO4 (LFP) battery made of lithiated P-HCNF@ZnO anode exhibits a high capacity of 175.3 mAh g−1 and a lower over-potential by 0.29 V than the reference sample. Analytical works and theoretical interpretations, elucidated that the Li metal anode made of the P-HCNF@ZnO significantly improves the performance of LMBs.

Equivariant Observers for Second-Order Systems on Matrix Lie Groups

This paper develops an equivariant symmetry for second order kinematic systems on matrix Lie groups and uses this symmetry for observer design. The state of a second order kinematic system on a matrix Lie group is naturally posed on the tangent bundle of the group with the inputs lying in the tangent of the tangent bundle known as the double tangent bundle. We provide a simple parameterization of both the tangent bundle state space and the input space (the fiber space of the double tangent bundle) and then introduce a semi-direct product group and group actions onto both the state and input spaces. We show that with the proposed group actions the second order kinematics are equivariant. An equivariant lift of the kinematics onto the symmetry group is derived and used to design nonlinear observers on the lifted state space using nonlinear constructive design techniques. The observer design is specialised to kinematics on groups that themselves admit a semi-direct product structure and include applications in rigid-body motion amongst others. A simulation based on an ideal hovercraft model verifies the performance of the proposed observer architecture.

Cryogenic fracture toughness of 3D random fibrous materials

This study aimed to evaluate the fracture toughness of three-dimensional random fibrous (3D RF) materials with 87% porosity and shallow surface cracks at room temperature (20 ℃) and cryogenic temperature (− 100 ℃). The ratios of crack length to specimen width of three-point-bending (3-p-b) specimens were 0.2 and 0.5, respectively. The experimental results revealed that the average fracture toughness KIC at − 100 ℃ was higher than that at 20 ℃. In addition, the experimental data were analysed using the boundary effect model (BEM), with almost all experimental data included in the upper and lower boundaries with 96% reliability, as specified by a normal distribution. Furthermore, based on the fracture toughness KQ computed using the formula of American Society for Testing Materials (ASTM), the expression of the fibre gap size G is derived. When the confidence level was 95%, no significant difference was observed in the fracture toughness model when the fibre gap size G was replaced with the average fibre spacing size D2 in the fracture toughness model. Thus, this study is expected to provide a reference for the safety assessment of the insulation layer of space shuttles at cryogenic temperatures.

On the boundedness of globally F-split varieties

This paper proposes the use of F-split and globally F-regular conditions in the pursuit of BAB type results in positive characteristic. The main technical work comes in the form of a detailed study of threefold Mori fibre spaces over positive dimensional bases. As a consequence we prove the main theorem, which reduces birational boundedness for a large class of varieties to the study of prime Fano varieties.

Biodegradable Polymer Electrospinning for Tendon Repairment.

With the degradation after aging and the destruction of high-intensity exercise, the frequency of tendon injury is also increasing, which will lead to serious pain and disability. Due to the structural specificity of the tendon tissue, the traditional treatment of tendon injury repair has certain limitations. Biodegradable polymer electrospinning technology with good biocompatibility and degradability can effectively repair tendons, and its mechanical properties can be achieved by adjusting the fiber diameter and fiber spacing. Here, this review first briefly introduces the structure and function of the tendon and the repair process after injury. Then, different kinds of biodegradable natural polymers for tendon repair are summarized. Then, the advantages and disadvantages of three-dimensional (3D) electrospun products in tendon repair and regeneration are summarized, as well as the optimization of electrospun fiber scaffolds with different bioactive materials and the latest application in tendon regeneration engineering. Bioactive molecules can optimize the structure of these products and improve their repair performance. Importantly, we discuss the application of the 3D electrospinning scaffold's superior structure in different stages of tendon repair. Meanwhile, the combination of other advanced technologies has greater potential in tendon repair. Finally, the relevant patents of biodegradable electrospun scaffolds for repairing damaged tendons, as well as their clinical applications, problems in current development, and future directions are summarized. In general, the use of biodegradable electrospun fibers for tendon repair is a promising and exciting research field, but further research is needed to fully understand its potential and optimize its application in tissue engineering.

Numerical study on the behavior and strength of concrete beam strengthening with fiber reinforced concrete jackets

The recent experimental results for slender reinforced concrete beams with a thin steel fiber reinforced concrete (SFRC) jacket have demonstrated their feasibility in enhancing the performance in terms of serviceability and ultimate limit states and strongly suggested the need for a comprehensive analysis to show the effect of important parameters. Within this context, the bond between reinforced concrete (RC) beams and SFRC jacket is an essential parameter to avoid any slippage failure before the beam achieves its shear capacity. The behavior of the bonded element is affected by slip at the interface between the old and new concrete. However, it is common in design to ignore slip and consider the bonded element monolithic. The values of slip and shear stress relation of the strengthened element are reviewed in this paper. In addition, an analytical procedure for predicting the distribution of slip along the interface between the initial beam and the new layer of concrete is presented. The research paper aims to develop a detailed three-dimensional (3D) finite element (FE) model for evaluating the structural performance of RC beams strengthened with SFRC jackets taking into accountthe effect of the bond between the beam and the jacket. It also aims to investigate the effect of significant parameters on the response of strengthened RC beams in shear. These parameters are as follows: jacket compressive strength (30, 60, and 85 MPa), fiber volume fraction (0.5, 1.0, 1.5, and 3.0%), jacket thickness (30, 40, 50, and 60 mm), and spacing between shear connectors (100, 200, and 500 mm). The proposed model's results were compared to those of previous experimental research. The analysis result showsgood agreement with the correlating experimental measurement. The parametric study results proved that increasing the volume fraction of fiber, jacket thickness, and compressive strength of the jacketincreases ductility and shear capacity. Increasing the spacing between shear connectors has no noticeable effect on shear capacity but prevents debonding. Finally, reference equations were made to study the behavior of RC beams strengthened with SFRC jackets, taking into accountthe effect of the bond between the beam and the jacket.

FRC-TOuNN: Topology Optimization of Continuous Fiber Reinforced Composites using Neural Network

In this paper, we present a topology optimization (TO) framework to simultaneously optimize the matrix topology and fiber distribution of functionally graded continuous fiber-reinforced composites (FRC). Current approaches in density-based TO for FRC use the underlying finite element mesh both for analysis and design representation. This poses several limitations while enforcing sub-element fiber spacing and generating high-resolution continuous fibers. In contrast, we propose a mesh-independent representation based on a neural network (NN) both to capture the matrix topology and fiber distribution. The implicit NN-based representation enables geometric and material queries at a higher resolution than a mesh discretization. This leads to the accurate extraction of functionally-graded continuous fibers. Further, by integrating the finite element simulations into the NN computational framework, we can leverage automatic differentiation for end-to-end automated sensitivity analysis, i.e., we no longer need to manually derive cumbersome sensitivity expressions. We demonstrate the effectiveness and computational efficiency of the proposed method through several numerical examples involving various objective functions. We also show that the optimized continuous fiber reinforced composites can be directly fabricated at high resolution using additive manufacturing.

Electrospun Nanomaterials Based on Cellulose and Its Derivatives for Cell Cultures: Recent Developments and Challenges.

The development of electrospun nanofibers based on cellulose and its derivatives is an inalienable task of modern materials science branches related to biomedical engineering. The considerable compatibility with multiple cell lines and capability to form unaligned nanofibrous frameworks help reproduce the properties of natural extracellular matrix and ensure scaffold applications as cell carriers promoting substantial cell adhesion, growth, and proliferation. In this paper, we are focusing on the structural features of cellulose itself and electrospun cellulosic fibers, including fiber diameter, spacing, and alignment responsible for facilitated cell capture. The study emphasizes the role of the most frequently discussed cellulose derivatives (cellulose acetate, carboxymethylcellulose, hydroxypropyl cellulose, etc.) and composites in scaffolding and cell culturing. The key issues of the electrospinning technique in scaffold design and insufficient micromechanics assessment are discussed. Based on recent studies aiming at the fabrication of artificial 2D and 3D nanofiber matrices, the current research provides the applicability assessment of the scaffolds toward osteoblasts (hFOB line), fibroblastic (NIH/3T3, HDF, HFF-1, L929 lines), endothelial (HUVEC line), and several other cell types. Furthermore, a critical aspect of cell adhesion through the adsorption of proteins on the surfaces is touched upon.

Atmospheric pressure plasma jet impinging on fiber arrays: Penetration pattern determined by fiber spacing

Atmospheric pressure cold plasmas have great potential for surface functionalization, and the interaction between the plasmas and fibers is essential to understand the underlying physics. In this Letter, the penetration pattern and mechanism of an atmospheric pressure plasma jet (APPJ) interacting with different spacing fiber scaffolds were studied by both experiment and modeling. The intensified charge coupled device images showed that APPJ induced a radial surface streamer on the windward side of the scaffold and another axial forward streamer on the opposite side. Propagation distance of both the radial and axial streamers diminished as the spacing decreased. Similar trends were predicted by a 2D fluid model. The simulation results indicated that the high electrical field carried by the streamer head in APPJ was allowed to pass through the gap for large spacing scaffold, while it was blocked by high intensity charges at small spacing. Instead, one axial streamer was generated in the latter case. The physical insight on the penetration mechanism of plasma jet interacting with fiber array in this Letter may contribute to improve treatment uniformity of plasma technology.

Repair of tendons treated with peracetic acid-ethanol and gamma irradiation by EDC combined with NHS: a morphological, biochemical and biomechanical study in vitro.

The purpose of this study was to investigate whether 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) combined with n-hydroxysuccinimide (NHS) can repair tendon damage caused by peracetic acid-ethanol and gamma irradiation sterilization. The semitendinosus tendons of 15 New Zealand white rabbits were selected as experimental materials, and the tendons were sterilized in a solution containing 1% (v/w) peracetic acid and 24% (v/w) ethanol. After 15kGy gamma irradiation sterilization, the tendons were randomly divided into three groups (n = 10). The tendons were repaired with EDCs of 0, 2.5 and 5mM combined with 5mM NHS for 6h, the tendons were temporarily stored at - 80 ± °C. The arrangement and spatial structure of collagen fibers were observed by light microscopy and scanning electron microscopy, the collagen type and collagen crimp period were observed under a polarizing microscope, and the collagen fibril diameter and its distribution were measured by transmission electron microscopy, from which the collagen fibril index and mass average diameter were calculated. The resistance of collagen to enzymolysis was detected by the free hydroxyproline test, and tensile fracture and cyclic loading tests of each group of tendons were carried out, from which the elastic modulus, maximum stress, maximum strain, strain energy density and cyclic creep strain were calculated. The obtained results showed that the gap between loose collagen fibers in the 0mM control group was wider, the parallel arrangement of tendons in the 2.5 and 5mM groups was more uniform and regular and the fiber space decreased, the crimp period in the 5mM group was lower than that in the 0mM group (P < 0.05), and the concentration of hydroxyproline in the 5mM group (711.64 ± 77.95μg/g) was better than that in the control group (1150.57 ± 158.75μg/g). The elastic modulus of the 5mM group (424.73 ± 150.96MPa) was better than that of the 0mM group (179.09 ± 37.14MPa). Our results show that EDC combined with NHS can repair damaged tendons after peracetic acid-ethanol and gamma radiation treatment, and 5mM EDC has better morphological performance, anti-enzymolysis ability and biomechanical properties than 2.5mM EDC.