Fiber Position Research Articles

Correcting Turbulence-induced Errors in Fiber Positioning for the Dark Energy Spectroscopic Instrument

Highly multiplexed, robotic, fiber-fed spectroscopic surveys are observing tens of millions of stars and galaxies. For many systems, accurate positioning relies on imaging the fibers in the focal plane and feeding that information back to the robotic positioners to correct their positions. Inhomogeneities and turbulence in the air between the focal plane and the imaging camera can affect the measured positions of fibers, limiting the accuracy with which fibers can be placed on targets. For the Dark Energy Spectroscopic Instrument, we dramatically reduced the effect of turbulence on measurements of positioner locations in the focal plane by taking advantage of stationary positioners and the correlation function of the turbulence. We were able to reduce positioning errors from 7.3 to 3.5 μm, speeding the survey by 1.6% under typical conditions.

High detail resolution cellulose structures through electroprinting

Electrospinning is a technique used to fabricate polymer fibers in micro- and nanoscales. Due to the large distance between the nozzle and collector, there is a limited positioning accuracy of electrospun fibers. To enhance the possibility of fabricating structures with micrometer placement, an electroprinting technique has been developed. By reducing the distance between the nozzle and the collector it is demonstrated that it is possible to get an improved control over fiber positioning which gives a possibility to fabricate designed 3D structures at the micron scale. In this study, cellulose acetate (CA) has been selected as a biomaterial to advance the 3D printing of membranes with possible use in separation applications. Various parameters, such as CA concentration and molecular weight, printing speed, printing pattern, applied voltage, etc. are evaluated with respect to printing control. Results indicate that by optimizing the printing parameters it is possible to print structures with inter- fiber distances down to 3 µm and fiber diameters at a sub-µm scale. This electroprinting development is promising for the fabrication of customized separation membranes. However, printing speed still remains a challenge.

The positioning of stress fibers in contractile cells minimizes internal mechanical stress

The positioning of stress fibers in contractile cells minimizes internal mechanical stress

Fully automated measurement of the spatial distribution of both fibre length and orientation from micro-CT images of short fibre reinforced polymers

The morphology of Short Fibre Reinforced Polymers (SFRPs) plays a fundamental role in determining their stiffness, strength and fracture behaviour. Measurements tools for the analysis of their microstructure are therefore of paramount importance. To this end, a fully automated algorithm able to segment single fibres from X-ray micro-computed tomography images was developed. This method was tailored to reconstruct the microstructure of large volumes of material; in particular, to acquire fibre length, position and orientation, even dealing with low-resolution images. The algorithm was tested on different specimens of short glass fibre-reinforced polyamide and it was validated comparing the fibre orientation with the one obtained with commercial software analysis and the fibre length with the experimentally determined one. Therefore, the proposed algorithm allows to easily identify microstructural trends without requiring the usual complex evaluating procedures.

Assessment of Yield and Economics under High Density Planting System in Cotton in Kachchh District of Gujarat, India

Cotton (Gossypium hirsutum L.) possesses a position of major fiber and cash crop, which plays vital role to sustain national economy. It provides the basic raw material (cotton fiber) to cotton textile industry. Gujarat contributes substantially to the national cotton area (24%) and productions (37%). A field experiment was carried out during the kharif seasons from 2017-18 to 2019-20 at farmers' fields through ICAR-CAZRI Krishi Vigyan Kendra Kachchh-II to evaluate the impact of frontline demonstrations (FLDs) on cotton productivity and profitability. During the experiment period, a total of 30 FLDs on high density planting system (HDPS) in cotton with the high-yielding variety GTHH-49 were demonstrated in a 12-hectare area across 6 villages in the Bhuj, and Nakhatrana talukas of Kachchh district. The improved variety GTHH-49 with a full package of practices was demonstrated in the plots, while existing technology was treated as the local check. Based on three years of data, the improved practice (IP) resulted in an average seed yield of 2868 kg ha-1, which was an increase of 13.35% compared to the local check yield of 2530 kg ha-1. The demonstrated technology showed an average extension gap, technology gap, and technology index of 338.33 kg ha-1, 631.67 kg ha-1, and 18.05%, respectively. The economic analysis of the demonstrations revealed the viability of the improved technology, with a net return of 101670.3 Rs. ha-1 and a benefit-cost ratio (BCR) of 3.24, compared to 84964.67 Rs. ha-1 and a BCR of 3.02 for local check. A wide range of extension and technology gaps had a detrimental influence on crop output and net returns in general. The results revealed that the adoption of the high-yielding variety with a full package of practices significantly increased cotton productivity and reduced both extension and technology gaps.

Optical fibre positioning and resonant frequency adjustment using intermittent optical feedback for pre-imaging calibration

Resonance operation of an optical fibre cantilever-based endoscopic scanner is crucial for distortion-free reconstructed images. While feedback control systems have been developed to ensure resonance operation, accurately measuring the location of the vibrating fibre cantilever tip remains challenging. Therefore, we proposed a passive aperture reflector as a sensing mechanism, placed in front of the fibre cantilever for intermittent feedback control. Using the characteristic of the pulse signal reflected from the scan extremities, the driving frequency and the position of the fibre cantilever can be adjusted. For frequency adjustment, both non-proportional and proportional control were conducted, and their results were compared. Besides that, the pulse width and their location with respect to the driving signal were utilised for location adjustment. The findings show that the proportional method with a high coefficient of 5.0 achieves fewer iterations to adjust the driving frequency and closely match it with the resonance frequency. Additionally, the presence of a pulse signal at both positive- and negative-going zero-crossings of the driving signal with similar pulse width ensures the cantilever is centred horizontally. Vertical centring can also be achieved by minimizing the pulse width. The simplicity and passive nature of the apertured metal plate mechanism offer advantages in accurately determining frequency and position.

A Combined Investigation of Bending Behavior of a SiC Fiber‐Reinforced Titanium Matrix Composite with Compressive and Tensile Tests

The study investigates the bending behavior and failure mechanisms of a titanium matrix composite reinforced with SiC fibers. The effects of nominal fiber volume fraction, testing temperature, and fiber position on bending behavior are evaluated. The results indicate that increasing the nominal fiber volume fraction from 19% to 50% improves average bending strength, reaching 2757 MPa at room temperature and 2596 MPa at 350 °C. Fiber position significantly influences bend strength, and composites with fibers on the concave side show greater strength than those with fibers on the convex side. Cracks in the composite specimen preferentially initiate from the bottom of the composite core rather than from the top, and fiber breakage under tensile stress is the dominant damage mechanism in the bend test. That is consistent with the lower tensile strength relative to the compressive strength of the composite.

Dynamic analysis and manipulation of self-starting single-pulse mode-locking in a Yb-doped fiber laser with Figure-9 all-normal-dispersion

The self-starting single-pulse mode-locked mechanisms in an all-normal-dispersion (ANDi) Figure-9 fiber laser are portrayed via an integrated simulation approach, which combines rate equations with the General Nonlinear Schrödinger Equation (GNLSE). The simulation results indicate that the mode-locking performances and pulse characteristics are significantly influenced by the splitting ratio, linear phase shift, gain, and asymmetric placement of gain fiber positions within the loop directly, providing effective quantified guidance for self-starting high-quality pulse generation. An experimental oscillation based on a nonlinear amplifying loop mirror (NALM) was established, operating under different widths of bandpass filters. Combining simulation for parameter optimization, the introduced linear phase shift and the coupling ratio were adjusted by changing the rotation angle of the combination wave plate to determine the optimal mode-locked operating point. A spectral bandwidth of 10.4 nm and a pulse duration of 17.5 ps, delivering 0.67 nJ of pulse energy, have been achieved in a modified mode-locked Yb-doped fiber laser.

Fluid-Solid Interaction Analysis for Developing In-Situ Strain and Flow Sensors for Prosthetic Valve Monitoring.

Transcatheter aortic valve implantation (TAVI) was initially developed for adult patients, but there is a growing interest to expand this procedure to younger individuals with longer life expectancies. However, the gradual degradation of biological valve leaflets in transcatheter heart valves (THV) presents significant challenges for this extension. This study aimed to establish a multiphysics computational framework to analyze structural and flow measurements of TAVI and evaluate the integration of optical fiber and photoplethysmography (PPG) sensors for monitoring valve function. A two-way fluid-solid interaction (FSI) analysis was performed on an idealized aortic vessel before and after the virtual deployment of the SAPIEN 3 Ultra (S3) THV. Subsequently, an analytical analysis was conducted to estimate the PPG signal using computational flow predictions and to analyze the effect of different pressure gradients and distances between PPG sensors. Circumferential strain estimates from the embedded optical fiber in the FSI model were highest in the sinus of Valsalva; however, the optimal fiber positioning was found to be distal to the sino-tubular junction to minimize bending effects. The findings also demonstrated that positioning PPG sensors both upstream and downstream of the bioprosthesis can be used to effectively assess the pressure gradient across the valve. We concluded that computational modeling allows sensor design to quantify vessel wall strain and pressure gradients across valve leaflets, with the ultimate goal of developing low-cost monitoring systems for detecting valve deterioration.

Performance Simulation of Muon Detectors Based on Structural Design and Array Layout of Plastic Scintillators

The performances of muon detectors have prominent effects on the accuracy and application scenario of muon imaging. Previous studies have paid more attention to the performance improvements of muon detectors in the assembly of imaging systems and optimization of imaging algorithms, while, the structural design and array layout of plastic scintillators in muon detectors have received less attention. In this work, the simulation models of plastic scintillator, wavelength-shifting (WLS) fibers, and muon source are constructed in the Geant4 software. On this basis, different factors affecting light collection efficiency (LCE) have been investigated, including muon hitting position, plastic scintillator cross-sectional shape and size, and WLS fiber size and position. Meanwhile, the influences of scintillator array layout, average width, and muon energy on the position resolution performance of the detector are investigated. The constructive results have been listed as follows: (a) the longitudinal length of the plastic scintillator unit, the shape and size of the WLS fiber, and the position of the WLS fiber have a large impact on the LCE. (b) The Right-angled triangle staggered layout is suitable for small-sized scintillators with single-energy muon hitting, and the Rhombus staggered layout is suitable for large-sized scintillators with multiple-energy muon hitting. This work provides theoretical support for the structural design and array layout of plastic Scintillators, and it has an important significance as a guide for the design of the subsequent muography system.

A scale-span method to characterize the mechanical property of BCF/PEEK considering uncertain structural characteristics

The focus of this study is exploring a scale-span characterization method to predict the mechanical properties of Braided Carbon Fiber Reinforced Poly Ether Ether Ketone (BCF/PEEK) considering structural uncertainty. Firstly, a complicated micro-scale Representative Volume Element (RVE) model that considers the random position and size of fiber was established via the developed Python script. Analogously, a mathematical expression adopted by the trust region algorithm was proposed to accurately describe the detailed cross-sectional shapes and fluctuation amplitude characteristics of BCF/PEEK for the sake of establishing the precision meso-scale RVE model. Then, the corresponding elastic properties that consider fiber volume fraction and fiber distribution location were characterized via the span-scale characterization method. Meanwhile, the influence of fiber bundle fluctuation amplitude and fiber volume fraction on the mechanical properties was investigated as well. In addition, the mechanical properties of BCF/PEEK with the change of the braid angle between warp and weft yarn were predicted via the established meso-scale RVE model. Finally, a series of experiments have been carried out. The maximum and minimum absolute prediction deviation of all elastic property parameters were only 4.07 % and 1.41 %, respectively, which verified the proposed scale-span characterization method can predict the mechanical properties of composites well.

Investigation of axial buckling behavior in composite laminates reinforced with S-glass fiber and epoxy featuring double cutouts

This research examines the impact of double cutouts on the critical buckling load of woven S-Glass/epoxy composite laminates. The study is divided into two parts: the first part involves comparisons, while the second part introduces numerical analyses. Initially, critical buckling loads of composite laminates without cutouts are determined using numerical and experimental methods. Subsequently, the results are compared to ensure consistency of critical load values obtained from the different methods. In the second part, the study investigates the effects of fiber angle, shape (square and circular), size, and position of cutouts in the composite plate using finite element analysis. The findings suggest that the shape and position of the cutout on the plate primarily influence the critical buckling load of the composite plates with circular cutouts, resulting in a relatively lower change in buckling load compared to square ones.

Design and evaluation of a pneumatic actuation unit for a wasp-inspired self-propelled needle.

Transperineal laser ablation is a minimally invasive thermo-ablative treatment for prostate cancer that requires the insertion of a needle for accurate optical fiber positioning. Needle insertion in soft tissues may cause tissue motion and deformation, resulting in tissue damage and needle positioning errors. In this study, we present a wasp-inspired self-propelled needle that uses pneumatic actuation to move forward with zero external push force, thus avoiding large tissue motion and deformation. The needle consists of six parallel 0.25-mm diameter Nitinol rods driven by a pneumatic actuation system. The pneumatic actuation system consists of Magnetic Resonance (MR) safe 3D-printed parts and off-the-shelf plastic screws. A self-propelled motion is achieved by advancing the needle segments one by one, followed by retracting them simultaneously. The advancing needle segment has to overcome a cutting and friction force, while the stationary needle segments experience a friction force in the opposite direction. The needle self-propels through the tissue when the friction force of the five stationary needle segments overcomes the sum of the friction and cutting forces of the advancing needle segment. We evaluated the prototype's performance in 10-wt% gelatin phantoms and ex vivo porcine liver tissue inside a preclinical Magnetic Resonance Imaging (MRI) scanner in terms of the slip ratio of the needle with respect to the phantom or liver tissue. Our results demonstrated that the needle was able to self-propel through the phantom and liver tissue with slip ratios of 0.912-0.955 and 0.88, respectively. The prototype is a promising step toward the development of self-propelled needles for MRI-guided transperineal laser ablation as a method to treat prostate cancer.

Optical transmission trajectories in single tapered fibers of TOFA by numerical simulation and experimental verification

Tens of millions or billions of single tapered fibers are independent optical transmission elements of tapered optical fiber array (TOFA) for imaging. The optical transmission trajectories of these single tapered fibers, which directly affect imaging qualities of TOFA, are rarely analyzed. This paper provides a method to numerically simulate it for fibers located at different positions along the radial direction of TOFA. The tapered curves of TOFA were firstly simulated by Finite Element Analysis (FEA) software and experimentally verified by the same preparation parameters. It is shown that the slope of tapered curve increases with stretching length. Meanwhile, the taper angle gets greater, and the profile of tapered deformation zone expands outward, while the radius of straight zone remains stable. Based on these, the optical transmission trajectory of single tapered fibers located from center to edge in TOFA was simulated, and then further verified by a self-developed instrument. Both simulation and experiment illustrate that the relative transmittance of single tapered optical fiber is decreased along the radial direction within the same TOFA. In comparison with the transmittance of the central axial fiber, the simulated and experimental unevenness on relative transmittance of peripheral fibers is within 7.11% and 9.74%, respectively. With the relative transmittance at the central position of the optical fiber being identical, the difference of relative transmittance (ΔT) between the simulation and experiment is gradually increased from center to peripheral regions along the radial direction of TOFA, reaching the maximum ΔT of 4.23%. The simulated results are well in agreement with the experimental ones.

Motion Planning for the Robotic Fiber Positioners of the Large Sky Area Multiobject Fiber Spectrocopy Telescope

The Large Sky Area Multi-Object Fiber Spectroscopy Telescope (LAMOST) is one of the most effective multiobject spectroscopic instruments. Its survey efficiency is guaranteed by simultaneously positioning multiple fibers via 4000 robotic fiber positioners (RFPs). With the further updates to LAMOST, the new-generation RFPs will be smaller, and the number of RFPs will increase to 5000. The RFPs are densely packed with shared working space. Thus, they may collide with each other, leading to them damaged and reducing the survey speed. In this study, we propose a new motion planning algorithm that prevents the collision of RFPs. To simplify the collision avoidance problem, we transform the motion planning process from a dynamic one into a static one by selecting one of the RFPs in each collision pair as the waiting robot. Accordingly, we design a method for choosing the waiting robot, and use a rapidly exploring random tree to plan a collision-free path for the waiting robot. However, there may be blocks between the waiting robots and their neighbors. Therefore, we also design methods to resolve these blocks. Simulations suggest that the proposed algorithm can prevent 98.4% of the collisions. About 99.9% of the positioners can reach their targets without collisions. Although developed for LAMOST, we believe that our algorithm can also be used for other instruments with equal-arm theta-phi positioners, such as the Dark Energy Spectroscopic Instrument.

NON-WOODEN RAW AS A SOURCE OF CELLULOSE FIBERS. USE PROSPECTS, PROBLEMS AND SOLUTIONS (REVIEW)

The article discusses various non-wood plants as sources of fibrous raw materials for the pulp and paper industry. The authors cite the main categories of non-wood fibrous raw materials: agricultural waste, naturally growing plants and industrial crops. Information is provided on the position of fibers in the plant: fibers of the inner part of the stem, bast (outer part of the stem) fibers, leaf fibers and fruit fibers, as well as methods for their isolation. Of the variety of non-wood plants, the authors highlight industrial hemp as the most promising raw material, having strong fibers and a high cellulose content. The use of non-timber raw materials has been found to help reduce pressure on forest resources and improve the environmental sustainability of pulp and paper production. Technological aspects of the production of paper products from non-wood raw materials are also considered. The advantages and disadvantages of using alternative raw materials, as well as its prospects, are given. The need for further research and development of new methods and technologies to optimize the efficiency of using non-wood raw materials in the pulp and paper industry is pointed out. In conclusion, a conclusion is drawn about the importance of using non-wood raw materials to reduce the negative impact of paper production on the environment and ensure the sustainable development of this industry.

Study on the Quasi-Ductile Fracture Behavior of Glubam: The Role of Fiber Distribution.

Cracking in fibrous composites is inevitable, and the fracture pattern is influenced by its fiber distribution. Bamboo fibrous composites have a distinct fiber distribution, which makes them an excellent material for studng the relationship between fiber distribution and fracture mode. Glued laminated bamboo is a bi-directional bamboo fibrous composite, which is called glubam for short. Its vertical thickness is about 28 mm, and the ratio of the number of longitudinal fiber layers to the number of transverse fiber layers is 4:1. This study conducted three-point bending fracture tests on single-edge notched specimens of glubam to investigate its mode-I fracture characteristics in the transverse vertical direction. The deformation curves show that the specimens still have the load-carrying capacity after reaching the maximum load, and the load shows a trend of step-like decrease, exhibiting a quasi-ductile fracture behavior. Overall, the fracture process can be divided into four stages, including linear, softening, quasi-ductile, and failure stages. In this study, based on certain assumptions, the prefabricated notch length a0 was adjusted according to the position of the transverse fibers. Subsequently, the non-linear elastic fracture mechanics method was employed to calculate the fracture parameters of glubam during the softening and quasi-ductile stages, including the fracture toughness KIC* and fiber tensile strength ft. The deviation of the fracture parameters between the two stages is within 10%, indicating that the correction of the a0 is correct. This indirectly proves that the staggered structure formed by longitudinal and transverse fibers is responsible for the quasi-toughness fracture of glubam. Finally, this study summarized and analyzed the quasi-ductile fracture behavior and found that materials or structures exhibiting quasi-ductile fracture behavior often possess a staggered structure. This staggered structure makes the crack in the form of semi-stable propagation, while the load decreases in a step-like manner.

Scalable, high-strength, wear-resistant, antibacterial polyethylene micro-nano fiber protective materials

Polyethylene (PE) fibers, known for their exceptional mechanical and protective properties, have found valuable applications in personal protective equipment during the COVID-19 pandemic. However, traditional PE fibers lack inherent antibacterial properties, making them susceptible to microbial contamination and potentially contributing to the secondary transmission of pathogens. Therefore, the development of antibacterial PE fibers holds paramount importance. Here, we successfully develop high-strength, wear-resistant, and antibacterial PE fibers by applying a dip-coating process with polylactic acid (PLA) solutions containing ZnO-Ag nanoparticles onto the surface of PE fibers. These antibacterial PE fibers exhibit an impressive antibacterial rate exceeding 99.9% against common bacteria, a tensile strength of 33.7 MPa, along with outstanding wear resistance, wearing comfort, and washing stability. Furthermore, continuous production of antibacterial PE nonwovens is achieved by combining roll-to-roll and dip-coating processes. Therefore, the excellent properties and industrial-scale production potential of antibacterial PE fibers position them with broad application prospects in the fields of medical protection, biochemical protection, and beyond.

Fluid–structure interaction simulation and optical fibre stress analysis of submarine cables in vortex‐induced vibration

AbstractUnder the current scouring, submarine cables are prone to be exposed, suspended, and even vortex‐induced vibration (VIV), threatening their mechanical and electrical properties. In this contribution, a finite element simulation model of 110‐kV single‐core optical fibre composite submarine cable is established. The natural frequency and resonant frequency of the model are obtained through wet mode analysis and harmonic response analysis. Then the VIV is simulated by the fluid–structure coupling method. Moreover, the stress extraction method of the torsional optical fibre position under the VIV is proposed. The results show that when the reduced speed is 2.57, the submarine cable appears beating vibration, which is composed of two vibrations with similar frequencies. When the reduced speed is 7.08, the vibration frequency is about 7.813 Hz, causing a rapid increase in vibration amplitude. The stress distribution of the torsional optical fibre presents a mirror image relationship at two moments separated by half a vibration cycle. Also, the frequency of stress change is the same as the frequency of VIV, which can judge whether the VIV occurs. The VIV range and position can be determined by the location where the stress changes the most.

Tensile, Dynamic Mechanical, and Vibration Behavior of Layering Sequence Design Effect of Glass Intertwined Natural Kenaf Woven Polymeric Laminates

ABSTRACT This study focuses on developing a fiber stacking of polymer laminate for high-impact load-absorbing applications, such as aircraft, automotive, and soundproofing structures. Therefore, the effect of high-strength fiber position effect on the tensile and dynamic behaviors of woven glass intertwined kenaf fiber thermoset composites was investigated in this research work. The tensile strength and dynamic mechanical properties of a hybrid stacking composite designed with maximum glass fiber, especially glass as an outer layer, are relatively higher. The outer layer of glass fiber is particularly effective in containing stress due to its high-strength characteristics, reducing stress transmission to the other core layers. The maximum storage of outer glass and inner kenaf woven stacking composite S1 were 7692.4 MPa, respectively. Besides, the most significant improvement in damping value was observed for the outer glass stacking kenaf (S1) composite compared to the all-other woven glass stacked composite. Furthermore, the composite with the outer glass layers and inner kenaf layers shows a more significant damping value due to the porous structure of the kenaf fibers, allowing for more excellent vibration energy dissipation. Overall, the stacking composites with a glass and kenaf layering arrangement exhibit good mechanical properties for high-impact load-absorbing applications.