Fiber Position Research Articles

From mixed to hydrodynamic regime in lubricated sliding of carbon fiber tows

Carbon fiber tows are used as reinforcement material in composite elements. To ensure mechanical integrity of the composite structure, it is important to ensure a good positioning of the carbon fibers in the mold during the manufacturing process. The positioning of the carbon fiber tows depends greatly on the friction with the mold. In the present paper, the friction between a carbon tow placed on a cylindrical pin rubbing against a rotating glass disk is experimentally studied in both dry and resin-lubricated conditions on a dedicated tribometer. The tests are performed for different loading levels and sliding speeds. The results are compared to numerical simulations taking into account contact mechanics and lubrication. The tows are modeled using a simple elastic foundation approach coupled with the Reynolds equation when the resin flow is considered. It appears that the impact of the deformability of the tow on its frictional behavior is significant. It conditions the transition between mixed and hydrodynamic lubrication regimes.

The Calibration of theta-phi Fiber Positioners Based on the Differential Evolution Algorithm

Robotic fiber positioner (RFP) arrays are commonly adopted in multiobject spectroscopic instruments. The positioning accuracy is a common but vital issue for RFP as inaccurate fiber placement may heavily affect the observation performance. The calibration of RFP can effectively improve the positioning accuracy. Least-square is a widely used calibration method. However, it has disadvantages, such as sensitivity to the initial values and calculation complexity. To improve the positioning accuracy and reduce the iteration moves, we propose a new calibration method based on the differential evolution algorithm and verify it by calibrating the RFP of the Large Sky Area Multi-Object Fiber Spectroscopy Telescope. We first build the kinematic models of the RFP based on the Denavit–Hartenberg matrix and geometry relationship. Then, we analyze the error components and present the proposed calibration algorithms. The experiments are done with the digital universal tool microscope 19JC and the errors are calculated using the distance between the positions of achieved and target. Results show that the proposed algorithm can achieve higher accuracy than the least-square method and the average positioning accuracy is improved by 78.94% after calibration. Combined with the “pulse reduction” strategy and close-loop compensation, after two moves, the positioners can place the fiber ends within 40 μm of the intended location. The proposed calibration method is also suitable for other similar theta-phi positioners.

Coverage and reliability improvement of copper metallization layer in through hole at BGA area during load board manufacture

Abstract The dimple of ball grid array (BGA) area with 70 mm × 70 mm size on load board for high performance integrated circuit final test is investigated by shadow moire at first, the dimple of BGA area decreases from 184.3 to 97.1 μm when six additional prepregs with 60 mm × 60 mm size are added at BGA area before hot lamination process. The micromorphology and stress/strain simulation are conducted to improve the coverage and reliability of copper metallization layer in through hole at that BGA area. The microcracks of electroless copper layer at the position of glass fiber and inner layer copper pad, which leads to serious crack after solder float, are well covered by subsequent electroplating copper layer. When the through holes at BGA area with 0.2 mm diameter and 7.0 mm depth are fabricated based on insulating dielectric material used for high-speed signal transmission, the simulation results point out that IT968 is better than M6G for the thermal shock reliability of through hole metallization layer. A load board vehicle with 126 layers and 8.3 mm thickness based on IT968 shows good interconnection structure reliability after 12 times 288°C solder float.

Design of continuous transition line pattern between layers of composite pressure vessel

To realize efficient and stable continuous transition between different winding process layers of composite pressure vessels. This article uses the non-geodesic winding equation to propose a transition layer design method for composite pressure vessel shells with circular cross-section core molds and ellipsoidal heads. Firstly, the fourth-order Runge–Kutta method is used to solve the non-geodesic stabilized winding pattern and then analyze different regions’ transition ability. Established a calculation model to determine the corresponding transition winding trajectory according to the known core mold shape and fiber position and carried out computer image simulation of different modes of transition layer patterns, and finally carried out experimental verification of 35 MPa composite pressure vessel based on the simulation. The results show that different regions of the core mold have different abilities to change different starting winding angles, and the design of the transition process layer based on this law can save the area needed for transition. This method realizes the smooth transition of different process layers; the fiber of the transition layer does not slip in the actual winding process, and the actual pattern of the winding is consistent with the simulation results, which saves 20.8% of the winding time, and effectively improves the automation of the composite pressure vessel winding process.

Research on the influence of intra-cavity dispersion on pulse characteristics of a quartic soliton fiber laser

Abstract We numerically investigate the influence of higher-order dispersion on the dynamics of quartic solitons in a passively mode-locked fiber laser. The simulation results show that the output pulse characteristics of the quartic soliton fiber laser are not only affected by the intra-cavity net dispersion but also related to the position of the single-mode fiber (SMF). For different intra-cavity net higher-order dispersion values, the quartic soliton undergoes multiple alternations between the stable single soliton state and pulsating state in the fiber laser, and the number and intensity of Kelly sidebands in the output pulse spectrum are significantly different. For different positions of the SMF, the dynamics of the quartic soliton are also different. In addition, we also observe two types of novel pulsation-creeping behavior and time shift. These findings provide new insights into the output characteristics of quartic solitons in fiber lasers.

Mesoscale modeling of flexural fracture behavior in steel fiber reinforced concrete

This paper presents a computational study on the flexural fracture behaviors of steel fiber reinforced concrete (SFRC). The focus is on investigating the impacts of various factors on SFRC, utilizing a discrete-continuum coupled finite element method. This method explicitly models each material phase, including coarse aggregates, mortar paste, steel fibers and interfacial transition zones (ITZs), allowing precise tracking of mesoscale cracking during bending. The simulation method is developed, calibrated and validated before conducting a parametric investigation. Critical factors considered include the spatial positioning of coarse aggregates and steel fibers, fiber content, length and diameter, and the bonding property of fiber-mortar ITZs. Results indicate that steel fibers modify crack development in notched beams, causing greater distortion in the primary crack. Increasing fiber content from 0 to 2% enhances flexural tensile strength but introduces more variability. Longer fibers initially increase strength, then decrease, while thicker fibers consistently reduce strength. Improving the bond between fibers and mortar does not substantially increase the load-bearing capacity of the beam. In conclusion, this study shows how the established approach enhances understanding of the mechanical responses of SFRC under flexural-fracture loading.

Distribution of neurovascular structures within the prostate gland and their relationship to complications after radical prostatectomy.

Radical prostatectomy remains the main choice of treatment for prostate cancer. However, despite improvements in surgical techniques and neurovascular sparing procedures, rates of erectile dysfunction, and urinary incontinence remain variable. This is due, at least in part, to an incomplete understanding of neurovascular structures associated with the prostate. The objective of this study was to provide a comprehensive, detailed histological overview of the distribution of nerves and blood vessels within the prostate, facilitating subsequent correlation of prostatic neurovascular structures with patients' clinical outcomes after radical prostatectomy. Neurovascular structures within the prostate were investigated in a total of 309 slides obtained from 15 patients who underwent non-nerve-sparing radical prostatectomy. Immunohistochemical staining was performed to identify and distinguish between parasympathetic and sympathetic nerves, whereas hematoxylin and eosin staining was used to identify blood vessels. The total number, density, and relative position of nerves and blood vessels were established using quantitative morphometry and illustrated using visualization approaches. Patient-specific outcome data were then used to establish whether the internal distribution of nerves and blood vessels within the prostate correlated with the nature and extent of complications after surgery. One-way analysis of variance tests and unpaired ttests were applied to establish statistically significant differences across the measured variables. Nerves and blood vessels were present across all prostatic levels and regions. However, their number and density varied considerably between regions. Assessment of the precise positioning of neurovascular structures revealed that the majority of nerve fibers were located within the dorsal and peripheral aspects of the gland. In contrast, blood vessels were predominantly located within ventral and dorsal midline regions. The number of intraprostatic nerves was found to be significantly lower in patients who recovered their continence within 12 months of surgery, compared to those whose recovery took 12 months or longer. We report an unexpected disconnect between the localization and positioning of nerve fibers and blood vessels within the prostate. Moreover, individual variability in the density of intraprostatic neurovascular structures appears to correlate with the successful recovery of urinary continence after radical prostatectomy, suggesting that differences in intrinsic neurovascular arrangements of the prostate influence postoperative outcomes.

The Application of Permanent Magnet Synchronous Motor with Small Electrical Time Constant in Fiber Positioner

With the development of cutting-edge multi-object spectrographs, fiber positioners located in the focal plane are being scaled down in size, and miniature hollow-cup Permanent Magnet motors are now being considered as a suitable replacement for Faulhaber Precistep stepper motors. However, the small electrical time constant of such coreless motors poses a challenge, as the problem of severe commutation torque ripple in a fiber positioner running a position loop has been tricky. To overcome this challenge, it is advised to increase the Pulse Width Modulation (PWM) frequency as much as possible to mitigate the effects of the current fluctuation. This must be done while ensuring adequate resolution of the PWM generator. By employing a voltage open-loop field-oriented control based on a modulation frequency of 1 MHz, the drive current only costs 25 mA under a 3.3 V power supply. The sine degree of phase current is immaculate, and the repeat positioning accuracy can reach 2 μm. Moreover, it is possible to further shrink the bill of devices and the layout area of the Printed Circuit Board, especially in size-sensitive applications. This device has been developed under the new generation of The Large Sky Area Multi-Object Fiber Spectroscopic Telescope.

Non-coincidence detection of fiber optic circulators based on Hertz-level frequency-shifting heterodyne interferometry

The fiber optic circulator in the form of point diffraction is a key component for coupling fiber optical path and spatial optical path in a laser Doppler vibration measurement system. The coupling efficiency and other performance parameters of fiber optic circulator are great significant for improving measurement accuracy and working distance of vibration measurement system. The conventional circulator coincidence detection methods include energy monitoring method and far-field coincidence monitoring method, which cannot be used to quantitatively analyze the fiber mismatch factors. Therefore, the consistency of the circulator coupling efficiency cannot be guaranteed. To solve these problems, a phase detection technology based on Hertz-level frequency-shifting heterodyne interferometry is proposed. The interferometry phase information is used to calculate the relative spatial positions of optical fibers, and this technology performs quantitative detection in the fiber alignment process. The interference wavefront formed by relative spatial positions of optical fibers is simulated and validated experimentally. The curves of coupling efficiency and wavefront PV value versus different kinds of alignment errors are simulated and analyzed. By fitting the interference wavefront with the Zernike polynomials, the correspondence between different kinds of alignment errors and Zernike coefficients is obtained. The value of Z2 (Zernike coefficient) can be used as the basis for judging whether there is transverse displacement in the Y direction. Similarly, Z3 corresponds to the transverse displacement in the X direction, Z4 corresponds to the longitudinal displacement in the Z direction and Z5 corresponds to the optical axis angle. Through this correspondence relationship, the quantitative separation and analysis of fiber mismatch factors are realized. The experimental results show that the accuracy of this method for measuring lateral displacement is better than 1μm. According to the phase diagram obtained from the experiment, Zernike coefficient fitting is performed. The lateral displacement deviation, longitudinal displacement deviation, and angular deviation are calculated by the coefficients of Z2 to Z5. The fiber adjustment mechanism corrects the transverse displacement deviation. It provides a new detection method for realizing fiber alignment and mismatch correction. Compared with the existing detection methods, the phase detection method based on Hertz-level frequency-shifting heterodyne interferometry solves the quantification problem of fiber coincidence adjustment. This method has the advantages of high measurement accuracy, compact detection structure and composition, and low detection cost. This method has great potential applications in the fields of optical fiber and spatial optical device alignment, optical system aberration detection, and planar wavefront detection.

Opto-hydrodynamic tweezers.

Optical fiber tweezers offer a simple, low-cost and portable solution for non-invasive trapping and manipulation of particles. However, single-fiber tweezers require fiber tip modification (tapering, lensing, etc.) and the dual-fiber approach demands strict alignment and positioning of fibers for robust trapping of particles. In addition, both tweezing techniques offer a limited range of particle manipulation and operate in low flow velocity regimes (a few 100 μm s-1) when integrated with microfluidic devices. In this paper, we report a novel opto-hydrodynamic fiber tweezers (OHT) platform that exploits the balance between the hydrodynamic drag force and optical scattering forces to trap and manipulate single or multiple particles of various shapes, sizes, and material compositions in a microfluidic channel. 3D hydrodynamic flow focusing offers an easy and dynamic alignment of the particle trajectories with the optical axis of the fiber, which enables robust trapping of particles with high efficiency of >70% and throughput of 14 particles per minute (operating flow velocity: 1000 μm s-1) without the need for precision stages or complex fabrication. By regulating the optical power and flow rates, we were able to trap single particles at desired positions in the channel with a precision of ±10 μm as well as manipulate them over a long range upstream or downstream with a maximum distance of 500 μm. Our opto-hydrodynamic tweezers offer an alternative to conventional optical fiber tweezers for several applications in physics, biology, medicine, etc.

Changes in DC Potential Difference and Carbon Fiber Position during Cyclic Bending of Unidirectional Prepreg

Changes in DC Potential Difference and Carbon Fiber Position during Cyclic Bending of Unidirectional Prepreg

Silk-based intelligent fibers and textiles: structures, properties, and applications.

Multifunctional fibers represent a cornerstone of human civilization, playing a pivotal role in numerous aspects of societal development. Natural biomaterials, in contrast to synthetic alternatives, offer environmental sustainability, biocompatibility, and biodegradability. Among these biomaterials, natural silk is favored in biomedical applications and smart fiber technology due to its accessibility, superior mechanical properties, diverse functional groups, controllable structure, and exceptional biocompatibility. This review delves into the intricate structure and properties of natural silk fibers and their extensive applications in biomedicine and smart fiber technology. It highlights the critical significance of silk fibers in the development of multifunctional materials, emphasizing their mechanical strength, biocompatibility, and biodegradability. A detailed analysis of the hierarchical structure of silk fibers elucidates how these structural features contribute to their unique properties. The review also encompasses the biomedical applications of silk fibers, including surgical sutures, tissue engineering, and drug delivery systems, along with recent advancements in smart fiber applications such as sensing, optical technologies, and energy storage. The enhancement of functional properties of silk fibers through chemical or physical modifications is discussed, suggesting broader high-end applications. Additionally, the review addresses current challenges and future directions in the application of silk fibers in biomedicine and smart fiber technologies, underscoring silk's potential in driving contemporary technological innovations. The versatility and sustainability of silk fibers position them as pivotal elements in contemporary materials science and technology, fostering the development of next-generation smart materials.

Effect of Two Different Polyethylene Fiber Positions on Fracture Resistance of Endodontic Treated Premolars: In vitro Comparative Study

Purpose: This study evaluated the effect of different polyethylene fibers positions on fracture resistance of endodontic treated premolars. Materials & Method: - 40 maxillary upper first premolars had been randomly divided in to 4 groups; (n=10). Except for control group, MOD cavity preparation with no steps were done within groups. After endodontic treatment and adhesive step and band application teeth restored with different techniques as follows: B-incremental with G- aenial posterior micro hybrid composite, C-circumferential Ribbond application (wallpapering) with incremental layering, D- bulkfill technique with ribbond reinforcement . Fracture test was measured using LARYEE device ( a computer controlled universal testing machine, China). Statistical analysis was done by One way ANOVA then LSD test to evaluate significance among groups. Results: The highest mean of fracture resistance in restored groups was recorded with group C (885 N) (wallpapering technique); while group D showed the lowest fracture resistance mean (678 N). Conclusion: positioning of polyethylene fibers circumferentially can enhance the fracture strength of endodontic treated teeth.

Distributed phase-matching measurement for dynamic strain and temperature sensing based on stimulated Brillouin scattering enhanced four-wave mixing

A Brillouin dynamic grating (BDG) can be used for distributed birefringence measurement in optical fibers, offering high sensitivity and spatial resolution for sensing applications. However, it is quite a challenge to simultaneously achieve dynamic measurements with both high accuracy and high spatial resolution. In this work, we propose a sensing mechanism to achieve distributed phase-matching measurement using a chirped pulse as a probe signal. In BDG reflection, the peak reflection corresponds to the highest four-wave mixing (FWM) conversion efficiency, and it requires the Brillouin frequency in the fast and slow axes to be equal, which is called the phase-matching condition. This condition changes at different fiber positions, which requires a range of frequency injection for the probe wave. The proposed method uses a chirped pulse as a probe wave to cover this frequency range associated with distributed birefringence inhomogeneity. This allows us to detect distributed phase matching for birefringence changes that are introduced by temperature and strain variations. Thanks to the single shot and direct time delay measurement capability, the acquisition rate in our system is only limited by the fiber length. Notably, unlike conventional BDG spectrum recovery-based systems, the spatial resolution here is determined by both the frequency chirping rate of the probe pulse and the birefringence profile of the fiber. In the experiments, an acquisition rate of 1 kHz (up to fiber length limits) and a spatial resolution of 10 cm using a 20 ns probe pulse width are achieved. The minimum detectable temperature and strain variation are 5.6 mK and 0.37 με along a 2 km long polarization-maintaining fiber (PMF).

A 4 mm Micro Servo Control System in Fiber Positioner

As multi-object spectrographs (MOSs) continue to evolve, a notable trend has emerged—the increasing accommodation of fiber positioners on ever-more compact focal planes. This progression has seen the traditional stepper motors being supplanted by more space-efficient miniature hollow-cup motors. A significant challenge faced in the employment of these 4 mm diameter motors is the absence of compatible angle sensors, resulting in reliance on open-loop control methods for positioning. Addressing this challenge, this paper introduces a novel miniature angle sensor designed specifically for 4 mm hollow-cup motors, and presents a newly formulated closed-loop control scheme, which leverages this sensor to achieve accurate positioning. This marks the first implementation of an angle closed-loop control system within a 4 mm miniature hollow-cup motor used in MOS fiber positioners. Experimental evidence suggests that this sensored closed-loop mode substantially improves upon the energy efficiency and precision of fiber positioner placement, compared with traditional open-loop stepper control methods. Furthermore, the integration of these microsensors mitigates collision risks during the concurrent operation of fiber positioners by deactivating the motor power supply to prevent potential damage to the system.

Effect of polyethylene fiber orientation on fracture resistance of endodontically treated premolars

Polyethylene fibers have been reported to improve the fracture resistance of endodontically treated teeth, but their optimal orientation is unclear. The purpose of this in vitro study was to evaluate the effects of different fiber positions and orientations on the fracture resistance of endodontically treated premolar teeth. One hundred endodontically treated maxillary premolars were divided into 2 groups according to the cavity design, mesio-occluso-distal and occluso-buccal, and each group was divided into 5 subgroups (n=10) according to the polyethylene fiber orientation on the pulpal floor: unidirectional horizontal (from mesial to distal), unidirectional vertical (from buccal to palatal), bidirectional (buccopalatal and mesiodistal), circular (around the walls), and without fibers (control group). The cavities were restored with fiber-reinforced composite resin and conventional composite resin. All the teeth were fractured with a universal testing machine and analyzed as catastrophic failure or reparable failure. A 1-way ANOVA was used to compare fracture strength values (α=.05). The tested groups with different fiber orientations showed significantly higher fracture load than the control group (P<.05). No statistically significant difference was observed among the fiber orientations (P>.05). Most of the favorable fractures were occlusal to the cemento-enamel junction, and adhesive failure were seen in the mesio-occluso-distal and occluso-buccal cavities. The highest percentage of unfavorable fractures and mixed failures was observed in the control group. The fiber orientation pattern in the mesio-occluso-distal and occluso-buccal cavities did not differ significantly in the fracture resistance of endodontically treated maxillary premolar teeth.

Fault Diagnosis of the LAMOST Fiber Positioner Based on a Long Short-term Memory (LSTM) Deep Neural Network

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) has been in normal operation for more than 10 yr, and routine maintenance is performed on the fiber positioner every summer. The positioning accuracy of the fiber positioner directly affects the observation performance of LAMOST, and incorrect fiber positioner positioning accuracy will not only increase the interference probability of adjacent fiber positioners but also reduces the observation efficiency of LAMOST. At present, during the manual maintenance process of the positioner, the fault cause of the positioner is determined and analyzed when the positioning accuracy does not meet the preset requirements. This causes maintenance to take a long time, and the efficiency is low. To quickly locate the fault cause of the positioner, the repeated positioning accuracy and open-loop calibration curve data of each positioner are obtained in this paper through the photographic measurement method. Based on a systematic analysis of the operational characteristics of the faulty positioner, the fault causes are classified. After training a deep learning model based on long short-term memory, the positioner fault causes can be quickly located to effectively improve the efficiency of positioner fault cause analysis. The relevant data can also provide valuable information for annual routine maintenance methods and positioner designs in the future. The method of using a deep learning model to analyze positioner operation failures introduced in this paper is also of general significance for the maintenance and design optimization of fiber positioners using a similar double-turn gear transmission system.

A Fiber Sliding-Orientation Based Micromechanics Failure Model for Melt-Blown Nonwovens.

The mechanical model of melt-blown nonwovens (MNs) serves as the foundation for performance optimization, which can offer helpful guidance for product material selection, structural design, and cost control. However, it is challenging to describe the micromechanics failure mechanism of MNs using the traditional mechanical model, which aims to match the model curve with the experimental result at the macrolevel. Herein, a micromechanics failure model for MNs based on sliding-orientation competition is developed. Through in situ observations of fiber position changes and the fluctuation of stress-strain curves, fiber sliding and orientation are introduced into the failure process of MNs. Due to fiber bonding and static friction, only orientation happens during the first stage of stretching. In dramatic contrast, the fibers will slide and orient in the second stage of stretching to change their positions in response to the external force. Sliding friction, fiber bonding, and static friction make up the stress of MNs, and the conflict of fiber sliding and orientation causes variations in the stress. The model has been successfully applied to polylactic acid (PLA) MNs, which proves the effectiveness of the model in MNs.

Satellite-to-ground optical downlink model using mode mismatching multi-mode photonic lanterns.

Photonics lanterns (PLs) provide an effective mode diversity solution to mitigate atmospheric turbulence interference in free-space optical communications (FSOC). This paper presents mode-mismatching multimode photonic lanterns (MM-PLs) for diversity receiver in satellite-to-ground downlink scenarios. Our study evaluates the coupling characteristics of the mode-selective PLs (MSPLs) and non-mode-selective PLs (NSPLs) for the influence of strong-to-weak turbulence and confirms that MSPLs outperform NSPLs under weak turbulence conditions. The research further explores the impact of fiber position error (FPE) on the spatial light-to-fiber coupling, including the optimal focal length deviation and lateral offset of receiving fiber devices. We have calculated and compared the coupling power and signal-to-noise ratio (SNR) of few-mode PLs (FM-PLs) and MM-PLs for various turbulence intensities. The results indicate that the optimal focal length tolerance, which corresponds to a decrease of approximately 1 dB in the average coupling power, is 2-3 m and 5-6 m for FM-PLs and MM-PLs, respectively. Furthermore, regardless of whether it is strong or weak turbulence, MM-PL exhibits a lateral offset tolerance exceeding 12 µm for a 0.5 dB drop in the mean coupled power, whereas the lateral offset tolerance of FM-PL is only 3 µm under weak turbulence. Additionally, the decrease in the average SNR of MM-PLs is gentle, only 0.67-1.16 dB at a 12 µm offset under weak turbulence, whereas there is a significant reduction of 6.50-8.49 dB in the average SNR of FM-PLs. These findings demonstrate the superiority of MM-PLs over FM-PLs in turbulence resistance and fiber position tolerance in the satellite-ground downlink.

Astrometric Calibration and Performance of the Dark Energy Spectroscopic Instrument Focal Plane

The Dark Energy Spectroscopic Instrument, consisting of 5020 robotic fiber positioners and associated systems on the Mayall telescope at Kitt Peak, Arizona, is carrying out a survey to measure the spectra of 40 million galaxies and quasars and produce the largest 3D map of the universe to date. The primary science goal is to use baryon acoustic oscillations to measure the expansion history of the universe and the time evolution of dark energy. A key function of the online control system is to position each fiber on a particular target in the focal plane with an accuracy of 11 μm rms 2D. This paper describes the set of software programs used to perform this function along with the methods used to validate their performance.