Fiber Position Research Articles

Embedded silicon carbide fiber sensor network based low-velocity impact localization of composite structures

Semi-conductive silicon carbide (SiC) fibers have excellent piezoresistive characteristics. Thus, SiC fibers not only can act as a sensing element but also a load bearing component in composite materials. In this study, embedded SiC fiber sensor network based low-velocity impact localization of composite structures was investigated. The SiC fiber sensor network was embedded into a composite panel during its fabrication process. By using the resistance changes of the embedded SiC fibers, impact signals were acquired, and reference impact signal based impact localization was performed. The reference data based impact localization was performed for various fiber configurations, and the effects of the embedment direction and position of the SiC fibers on the impact localization performance according to the embedment directions of SiC fiber sensors were compared and investigated. When the SiC fiber sensors are embedded in the direction of the reinforcing fibers, they can act as both the load bearing component and sensing element. On the other hand, when the embedment direction and position of the SiC fiber sensors were limited or constrained, the impact localization performance was influenced by the embedment direction and position of the SiC fibers. However, the impact localization performance was able to be improved through adjustment of the SiC fiber embedment direction, SiC fiber position, and mutual compensation between the SiC fibers. Consequently, the impact localization of the composite structure using an embedded SiC fiber network was successfully performed.

Purge-assisted and temperature-controlled headspace solid-phase microextraction combined with gas chromatography–mass spectrometry for determination of six common phthalate esters in aqueous samples

This study describes a novel procedure, namely, purge-assisted and temperature-controlled headspace solid phase microextraction combined with gas chromatography/mass spectrometry, which is used to determine six phthalate esters in aqueous samples. The optimum conditions for obtaining extraction efficiency, such as the extraction fiber type, extraction temperature, nitrogen gas purging flow rate, addition of salts, extraction time, headspace condenser cooling temperature, sample stirring rate, and fiber position parameters were investigated by using single-factor experiment (one-factor-at-a-time) and orthogonal experimental design (OED) methods. Under the optimal conditions, the linear range of detection of the proposed method was 0.2–50 ng/mL with coefficients of determination between 0.992 and 0.995. Limits of detection for six phthalate esters were 0.04–0.18 ng/mL. The application of the proposed method for the determination of trace phthalate esters in real samples was investigated by analyzing bottled water sample and brewed hot coffee successfully.

Probabilistic fibre-to-target assignment algorithm for multi-object spectroscopic surveys

Context. Several new multi-object spectrographs are currently planned or under construction that are capable of observing thousands of Galactic and extragalactic objects simultaneously. Aims. In this paper we present a probabilistic fibre-to-target assignment algorithm that takes spectrograph targeting constraints into account and is capable of dealing with multiple concurrent surveys. We present this algorithm using the 4-m Multi-Object Spectroscopic Telescope (4MOST) as an example. Methods. The key idea of the proposed algorithm is to assign probabilities to fibre-target pairs. The assignment of probabilities takes the fibre positioner’s capabilities and constraints into account. Additionally, these probabilities include requirements from surveys and take the required exposure time, number density variation, and angular clustering of targets across each survey into account. The main advantage of a probabilistic approach is that it allows for accurate and easy computation of the target selection function for the different surveys, which involves determining the probability of observing a target, given an input catalogue. Results. The probabilistic fibre-to-target assignment allows us to achieve maximally uniform completeness within a single field of view. The proposed algorithm maximises the fraction of successfully observed targets whilst minimising the selection bias as a function of exposure time. In the case of several concurrent surveys, the algorithm maximally satisfies the scientific requirements of each survey and no specific survey is penalised or prioritised. Conclusions. The algorithm presented is a proposed solution for the 4MOST project that allows for an unbiased targeting of many simultaneous surveys. With some modifications, the algorithm may also be applied to other multi-object spectroscopic surveys.

Prediction of mechanical properties of high strength steel fiber reinforced concrete with multiple regression technique

High strength steel fiber reinforced concrete which has cube compressive strength greater than 60 N/mm2 was prepared with OPC 53 grade cement confirming IS 269. Sand passing through IS sieve 4.75mm and retaining on IS sieve 150 micron was used in the investigation. Steel fiber with aspect ratio 80 reinforced randomly and at one third position from top of the concrete surface. The percentage of steel fiber varies from 0.5%, 1.0% and 1.5% by volume of concrete specimen. The percentage of silica fume varies from 5%, 10% and 15% by weight of cement used in concrete. Mechanical properties of concrete such as compressive strength, flexural strength were investigated for both the position of steel fiber in concrete. A multiple regression model was employed to predict the mechanical properties of HSSFRC. The regression analysis was performed based on the relationships between the independent variables and the dependent variables. Scatter plot was used to determine the relationship between predictor and criterion variables. The relationship between dependant and independent variable is explained by the magnitude (or the strength) and the direction of the relationship. The magnitude of relationship was calculated using “CORRELATION” formula, which gives the strength of the relationship. The actual shape of the curve determines the direction of the relationship.

Direct writing of silver microfiber with precise control on patterning for robust and flexible ultrahigh-performance transparent conductor

Ultrafine silver fiber is an alternative to commercial indium tin oxide (ITO) as a new-generation flexible transparent conductor that can be used in flexible electronics. However, its primary limitation is the unrepeatable optoelectronic properties due to the disordered distribution of silver fibers. In this work, we report the in-situ direct writing of the silver microfiber pattern with high conductivity and transparency to attain a flexible transparent conductor. The silver network is composed of silver microfibers, which can be artificially designed and regularly patterned under the precise control of the fiber position and shape; this is crucial for regulating its optoelectronic properties. Herein, a high-performance conductor is achieved in the silver network with high stability. This novel conductor has a sheet resistance of 2 Ω sq−1 at 90% transparency, which corresponds to a high Figure of merit σdc/σopt = 1742. The in-situ direct writing technique developed here is distinct from other fabrication methods because it requires no transfer steps, templates or heating. Further, this silver network is integrated into a light-printable rewritable device, and can be used as a wearable heater; this heater when driven by a 1.5 V battery attains a temperature of up to 55.6 ℃. Therefore, in-situ direct writing is expected to offer a new platform for facile, scalable, and ultralow-cost production of high-performance metal networks for flexible transparent conductors.

Photobiomodulation by diffusing optical fiber on spinal cord: A feasibility study in piglet model.

Previous studies on spinal cord injury (SCI) have confirmed that percutaneous photobiomodulation (PBM) therapy can ameliorate immunoinflammatory responses at sites of injury, accelerate nerve regeneration, suppress glial scar formation and promote the subsequent recovery of locomotor function. The current study was performed to evaluate a large-animal model employing implanted optical fibers to accurately irradiate targeted spinal segments. The method's feasibility and irradiation parameters that do not cause phototoxic reaction were determined, and the methodology of irradiating the spinal cord with near-infrared light was investigated in detail. A diffusing optical fiber was implanted above the T9 spinal cord of Bama miniature pigs and used to transfer near-infrared light (810 nm) onto the spinal cord surface. After daily irradiation with 200, 300, 500 or 1000 mW for 14 days, both sides of the irradiated area of the spinal cord were assessed for temperature changes. The condition of the spinal cord and the position of optical fiber were investigated by magnetic resonance imaging (MRI), and different parameters indicating temperature increases or phototoxicity were measured on the normal spinal cord surface due to light irradiation (ie, heat shock responses, inflammatory reactions and neuronal apoptosis), and the animals' lower-limb neurological function and gait were assessed during the irradiation process. The implanted device was stable inside the freely moving animals, and light energy could be directly projected onto the spinal cord surface. The screening of different irradiation parameters preliminary showed that direct irradiation onto the spinal cord surface at 200 and 300 mW did not significantly increase the temperature, stress responses, inflammatory reactions and neural apoptosis, whereas irradiation at 500 mW slightly increased these parameters, and irradiation at 1000 mW induced a significant temperature increase, heat shock, inflammation and apoptosis responses. HE staining of spinal cord tissue sections did not reveal any significant structural changes of the tissues compared to the control group, and the neurological function and gait of all irradiated animals were normal. In this study, we established an in-vivo optical fiber implantation method, which might be safe and stable and could be used to directly project light energy onto the spinal cord surface. This study might provide a new perspective for clinical applications of PBM in acute SCI.

Optical test procedure for characterization and calibration of robotic fiber positioners for multiobject spectrographs

The recent burgeoning interest in massive multiobject spectroscopy has pushed the development of massive optical fiber positioning systems. These systems rely on precise fiber placement to detect the light spectra of many stars and galaxies. One successful approach is the use of robotic fiber positioners, which allow one to automate and scale up observations. However, due to the need for high precision and accuracy, each positioner must be calibrated and verified to comply with the requirements. The calibration measurements are nontrivial, and the large number of the robotic positioners up to thousands can lead to a prohibitively long time for calibration. We describe and validate an optical calibration setup and procedure for robotic fiber positioning systems. Based on the measurements results, we have developed models describing the behavior of the positioners and we introduce new performance metrics that allow one to verify the stringent positioner specifications and furthermore help to identify and analyze design and manufacturing flaws.

A Model to Study Myelinated Fiber Degeneration and Regeneration in Human Skin.

To describe morphological changes associated with degeneration and regeneration of large fibers in the skin using a model of chronic compression of the median nerve. We studied cutaneous innervation in 30 patients with chronic compression of the median nerve at the wrist. Before surgery, we assessed the symptom severity and performed neurography, quantitative sensory testing, and analysis of nerve morphology and morphometry in skin biopsies from the third digit fingertip. Fifteen patients repeated all tests 12 months after the surgery. Thirty age- and sex-matched healthy subjects were included in the study. Clinical and neurophysiological basal assessment showed a moderate involvement of the median nerve. Quantitative sensory testing showed abnormal findings. The density of intraepidermal nerve fibers and intrapapillary myelinated endings was reduced. Myelinated fibers showed caliber reduction and nodal elongation. Meissner corpuscles had normal density but were located deeper in the dermis and their capsule appeared partially empty. During follow-up, patients exhibited a positive clinical and neurophysiological outcome. Quantitative sensory testing improved. Intraepidermal nerve fibers and intrapapillary myelinated endings remained unchanged, but the caliber of intrapapillary myelinated endings was increased. The neural component of the Meissner corpuscle filled the capsule of the mechanoreceptors that remained deeper in the dermis. The position of vasoactive intestinal peptide-immunoreactive fibers was more superficial compared to the basal assessment and controls. We recognized and quantified the pathological changes associated with nerve degeneration and regeneration in skin and proposed new parameters that may increase the diagnostic yield of skin biopsy in clinical practice. Ann Neurol 2020;87:456-465.

Distributed optical fiber temperature sensor based on self-compensation of fitting attenuation difference

The temperature error caused by the essential loss and the additional loss of Stokes light and anti-Stokes light widely exist in the distributed optical fiber temperature sensor (DTS). According to the temperature demodulation principle of the DTS, a method of fitting the attenuation difference between Stokes light and anti-Stokes light is proposed, which can realize the temperature self-compensation to reduce the temperature measurement error. Two parts at the different positions of the sensing fiber are regarded as the reference section and the temperature measuring section, respectively. The optical signal of the reference section is used as a parameter when demodulating the temperature and fitting the attenuation difference, and the attenuation difference between the Stokes light and the anti-Stokes light is multi-order fitted by the optical signal of the temperature measuring section, then the multi-order fitting results are used to demodulate the temperature for reducing the temperature error caused by the essential loss and additional loss of the Stokes light and anti-Stokes light, in order to implement the preliminary correction of the temperature. Three groups of the different measuring temperature values at the same position of the optical fiber as well as their corresponding signal values are taken in calculation for eliminating the Rayleigh noise, and the relationship of Rayleigh noise with fiber length and temperature are analyzed, and thus further calculating the Rayleigh noise based on the fitting attenuation difference. The influence of the multi-order attenuation difference on the error in temperature measurement and that on the elimination of the Rayleigh noise are compared with each other, and the Rayleigh noise error caused by the essential loss and additional loss of the Stokes light and anti-Stokes light are reduced, then the temperature is corrected again by eliminating the Rayleigh noise. The effect of the multi-order attenuation difference fitting result on the temperature measurement error and on the elimination of Rayleigh noise are analyzed and compared with each other, then the optimal fitting order is obtained. After fitting the additional error at the temperature measurement section that is caused by the additional loss at the reference section, the temperature compensation is carried out by the fitting result, then the final temperature correction is completed. The experimental results show that the temperature correction effect is best by using the first-order linear fitting results in a temperature range of 30－90 ℃, and the temperature measurement error is reduced from 10.50 ℃ to 0.90 ℃ after being corrected three times.

Improving the measurement of thread parameters by use of corundum elements

Considered an advanced method of the three wires to measure the average diameter dav and pitch P of the thread using three elements corundum (synthetic sapphire, sapphire, ruby): two fibers and tip with the ability to visualize and measure the size of the contact zone with the product to calculate the contact elastic deformation. It is proposed to use two fibers incoherent and one coherent interferometers to measure the position of corundum fibers and the tip. A method for calculating the diameter dav and pitch P of the thread based on the results of interferometer measurements by using the compensation of contact elastic deformations is presented.

Experimental and numerical study on free vibration of cracked woven fiber glass/epoxy composite beam

Composite beams are generally utilized in machinery structures with high-speed velocity, aircraft, and lightweight structures because of their high stiffness-to-weight proportions, a high degree of resistance to corrosion, tailor ability, and fatigue. Crack is one of the most critical damages in composite material as it greatly reduces the stiffness and strength of the member. These damages are a prime cause of increasing the vibration amplitude that leads to catastrophic failures. Structures are frequently exposed to dynamic loads during their administration life. So the assessment of the dynamic properties of cracked composite beams is of considerable technical importance and in this way, the subject of the present investigation. In the present study, changes in natural frequencies of industry-driven woven fiber Glass/Epoxy composite bar with transverse cracks are recorded numerically and experimentally. Finite element method (FEM) is utilized to explore the free vibration of the cracked composite beam. The FE model is created utilizing an eight-noded two-dimensional quadratic isoparametric component with 3 degrees of freedom for each node. The numerical analysis is done through the solution of the beam equations for the Eigenvalues accounting for shear deformation. FE software ANSYS is employed for simulation of free vibration. The experimental tests are done by utilizing a hammer test and the frequency response function (FRF) is shown on FFT analyzer. The numerical outcomes acquired utilizing ANSYS are approved with the trial results. The impacts of fiber orientation, crack depth and positions on the frequencies are investigated about its support in applied fields. The recorded test and numerical results agreed on the significant effects of crack location and depth on the natural frequencies of the laminated beam. The results show that the increase in fiber orientation considerably reduces the natural frequencies of the laminated composite beam.

Precision control of miniature SCARA robots for multi-object spectrographs

Advances in astronomy led to the demand for measuring the spectra of multiple night sky objects simultaneously. Some of these Multi-Object Spectrographs use robotic systems that position optical fibers in the focal plane of the observing telescope. These systems rely on precise fiber placement in order to collect the light spectra of faint stars and galaxies. Here, we present how to design, control, and operate micro SCARA-like robots to position optical fibers to micrometer precision. As an illustrative example, we show the design and performance results of the SDSS-V fiber positioner, which has been build for the Apache Point Observatory and the Las Campanas Observatory with 500 units for each telescope.

Optimal target assignment for massive spectroscopic surveys

Robotics have recently contributed to cosmological spectroscopy to automatically obtain the map of the observable universe using robotic fiber positioners. For this purpose, an assignment algorithm is required to assign each robotic fiber positioner to a target associated with a particular observation. The assignment process directly impacts on the coordination of robotic fiber positioners to reach their assigned targets. In this paper, we establish an optimal target assignment scheme which simultaneously provides the fastest coordination accompanied with the minimum of colliding scenarios between robotic fiber positioners. In particular, we propose a cost function by whose minimization both of the cited requirements are taken into account in the course of a target assignment process. The applied simulations manifest the improvement of convergence rates using our optimal approach. We show that our algorithm scales the solution in quadratic time in the case of full observations. Additionally, the convergence time and the percentage of the colliding scenarios are also decreased in both supervisory and hybrid coordination strategies.

中心开孔型四象限探测器光纤定位闭环控制方法

中心开孔型四象限探测器光纤定位闭环控制方法

中心开孔型四象限探测器光纤定位闭环控制方法

中心开孔型四象限探测器光纤定位闭环控制方法

Energy scalability of the dissipative soliton in an all-normal-dispersion fiber laser with nonlinear amplifying loop mirror

We numerically and experimentally report on a high-energy all-normal-dispersion Yb-doped fiber laser with a nonlinear amplifying loop mirror (NALM) acting as the mode-locker. Numerical simulations of the dynamic evolution of dissipative solitons in this structure indicate that the position of gain fiber in the loop mirror plays a key role in promoting pulse energy. Without significant Raman scattering effect, pulse trains with energy and average output power of 22 nJ and 191 mW, respectively, whose duration can be de-chirped to 195 fs, were experimentally obtained from the all-PM-fiber cavity. In addition, the multi-pulsing phenomena at different positions of gain fiber in the loop mirror limits the further increasing of the pulse energy. In this paper, both simulation and experiment are in good qualitative agreement, which provides a method for the mode-locked fiber laser with NALM to control and improve the output properties.

Effect of interface properties on micromechanical damage behavior of fiber reinforced composites

This paper investigates the micromechanical damage behavior of carbon-epoxy composite on the transverse tensile of representative volume elements (RVEs) with various fiber volume fractions. A new algorithm is developed to generate the random distribution of fibers in the RVE, and it is possible to create fiber distributions with high fiber volume fractions. The fibers and matrix are considered linear elastic and elastoplastic with progressive damage criterion, respectively. Fiber-matrix debonding and matrix crack are considered as the dominant damage modes. The normal cohesive properties distribution is applied for interfaces between fibers and the matrix in order to achieve a more realistic microstructure. To investigate the effect of the position of fibers with the weakest cohesive strengths, sensitivity analyses concerning the different arrangements of specific normal cohesive properties on the RVE’s strength are performed. Moreover, the effects of different damage parameters, such as random fiber distributions and various cohesive parameters on the overall damage behavior of the RVE, are described in detail. It is revealed that the application of a normal cohesive distribution sharply reduces the maximum strength of the RVE and shifts the strain of damage initiation point and crack propagation path.

Effect of glass fiber non-dental’s length and position on the flexural strength of FRC

Glass fiber non-dental has a similar composition to E-glass fiber dental that commonly used as fiber reinforced composite (FRC) materials in resin bonded prosthesis. Fiber effectiveness can be determined by the length and the position. The aim of this study was to examine the effect of glass fiber non dental’s length and position on the flexural strength of FRC in resin bonded prosthesis. This study has been done used 36 FRC samples with beam shaped (15 mm x 2 mm x 2 mm). Fiber reinforced composite samples were consisted of 9 groups (a combination between length: 4 mm, 6 mm, and 12 mm and position: compression, neutral, tension zone). The flexural strength was tested by universal testing machine and statistically analyzed using two-way ANOVA (p<0.05). The result showed that the lowest (compression, 4 mm) and the highest (tension, 12 mm) flexural strength were 104.30 ± 13.90 MPa and 166.18 ± 8.59 MPa. The two-way ANOVA test showed that variation of position, length, and interaction between placement-length had a significant effect on the flexural strength (p<0.05). The conclusion of this study was fiber position on compression zone with 4 mm length had the lowest flexural strength. In addition, fiber position on tension zone with 12 mm length had the highest flexural strength.

The influence of interaction between NSM and internal reinforcements on the structural behavior of upgrading RC beams

In this paper, the effect of interaction between near surface mounted (NSM) strips and internal reinforcement on the structural behavior of upgrading RC beams has been studied. The position, arrangement and area of NSM glass fiber reinforced polymer (GFRP) strips have been examined experimentally. Six strengthened beams in addition to one control beam were tested in flexural until failure. The load carrying capacity, deflections and the mode of failure of strengthened beams were recorded. The experimental results showed that the installed NSM GFRP side by side has a lower interfacial stress than those installed separated. This improvement is more obvious in the case of NSM strips installed near the internal reinforcement. Furthermore, the installed NSM strips in deep groove experienced higher load carrying capacity than those installed in shallow groove for both patterns. The installation of the NSM GFRP strips in deep grooves using epoxy may be delay or prevent the peeling/debonding failure. The ultimate load of the beam upgraded with one NSM strip adjacent to the stirrups (in deeper groove) is about 1.5 times that of one NSM strip installed near the bottom surface of the beam. This ratio decreased with increasing the area of NSM GFRP strips.

The Vastus Medialis Insertion Is More Proximal and Medial in Patients With Patellar Instability: A Magnetic Resonance Imaging Case-Control Study.

Background:The anatomy and function of the quadriceps muscle play a role in patellofemoral stability. Few studies have evaluated anatomic differences in the vastus medialis between patients with and without patellar instability.Purpose:To compare the anatomy of the vastus medialis using magnetic resonance imaging in patients with patellar instability to a control group.Study Design:Cross-sectional study; Level of evidence, 3.Methods:A group of patients with patellar instability were sex-matched with a control group with anterior cruciate ligament tears, meniscal injuries, or sprains; patients younger than 15 years were excluded. The anatomy of the vastus medialis was examined by the distance between the distal origin of the vastus medialis in the femur and the medial femoral condyle, the distance from the proximal pole of the patella to the most distal insertion of the muscle and its ratio to the length of the articular surface of the patella, and a qualitative description of the insertion position of the muscle fibers (directly in the patella or the medial retinaculum).Results:Both groups comprised 78 knees (48 female; 61.5%). The mean age in the control and patellar instability groups was 30.2 ± 7.8 years and 25.6 ± 7.5 years, respectively (P = .001). The distance from the vastus origin to the condyle was 27.52 ± 3.49 mm and 26.59 ± 3.43 mm, respectively (P = .041); the distance from the proximal pole of the patella to the most distal muscle insertion was 17.59 ± 5.54 mm and 15.02 ± 4.18 mm, respectively (P < .001); and the ratio of this distance to the joint surface was 0.586 ± 0.180 and 0.481 ± 0.130, respectively (P < .001). In 75.6% of knees in the patellar instability group, the insertion of the vastus was into the medial retinaculum and not into the patella compared with 52.6% in the control group (P = .003; odds ratio, 2.8).Conclusion:The distal insertion of the vastus medialis differed in knees with patellar instability, with a more proximal insertion and less patellar coverage relative to controls, and was more frequently found in the retinaculum instead of directly in the patella.