Axial Misalignment Research Articles

Analysis of characteristics of few-mode fiber fusion splicing under dynamic spatial modecrosstalk.

In this paper, an analytical model of the fusion splicing loss of few-mode fiber (FMF) under the condition of dynamic crosstalk is proposed. Under different dynamic spatial modal crosstalk caused by fusion mismatches and rotation angles, we analyze the variation trend of the fusion splicing loss characteristics of FMF with LP01,LP11a, and LP11b, respectively. Simulation results show that under the condition of axial misalignment introducing modal crosstalk, the splice loss of the LP11a and LP11b modes is higher than that of LP01. On the other hand, the modal crosstalk caused by rotation angles makes the fusion splice loss of LP01 present symmetrical distribution, and the loss of fusion splice of LP01 is maximum at 45°. When rotating from 0° to 90°, for LP11a and LP11b modes, the fusion loss of LP11a decreases gradually, while the loss of LP11b increases gradually. Both are in a symmetrical distribution. Meanwhile, we build an FMF fusion splice loss measurement system based on photon lanterns and FMF circulators. The experimental results show that it is consistent with the simulation results, and the experimental and simulation results confirm the feasibility of the fusion splice fault loss analysis modal under dynamic crosstalk conditions.

Spiral Bevel Gears Nonlinear Vibration Having Radial and Axial Misalignments Effects

In gear transmissions, vibration causes noise and malfunction. In actual applications, misalignments contribute to intensifying the destructive effect of vibrations. In this paper, the nonlinear dynamics of a spiral bevel gear pair, with small helix angle, considering different misalignments, are deeply investigated. Axial misalignment, radial misalignment, and the combination of these two types are considered in this study. The governing equation is numerically solved through an implicit Runge–Kutta scheme. Since the main goal of this study is the analysis of the dynamic scenario, the mesh stiffness of the gear pair is obtained from the literature. The dynamical system is nonlinear and time-varying; it is analyzed through time responses, phase portraits, Poincaré maps, and bifurcation diagrams. Results show that, among the considered three cases with different types of misalignments, the spiral bevel gear with axial misalignment is the worst destructive case; aperiodic, subharmonic, and multiperiod responses are observable for this case. It is interesting that the chaotic responses for the case, having both types of misalignments, are less likely for the case with axial misalignment, only.

The muscle M3 x-ray diffraction peak and sarcomere length: No evidence for disordered myosin heads out of actin overlap.

X-ray diffraction studies of muscle have provided a wealth of information on muscle structure and physiology, and the meridian of the diffraction pattern is particularly informative. Reconditi et al. (2014. J. Physiol.https://doi.org/10.1113/jphysiol.2013.267849) performed superb experiments on changes to the M3 meridional peak as a function of sarcomere length (SL). They found that the M3 intensity dropped almost linearly as sarcomere length increased at least to about SL = 3.0 µm, and that it followed the same track as tension, pointing toward zero at the end of overlap at ∼3.6 µm. They concluded that, just as tension could only be generated by overlapped myosin heads, so ordered myosin heads contributing to the M3 intensity could only occur in the overlap region of the A-band, and that nonoverlapped heads must be highly disordered. Here we show that this conclusion is not consistent with x-ray diffraction theory; it would not explain their observations. We discuss one possible reason for the change in M3 intensity with increasing sarcomere length in terms of increasing axial misalignment of the myosin filaments that at longer sarcomere lengths is limited by the elastic stretching of the M-band and titin.

Influence of frosted haptics on rotational stability of toric intraocular lenses

We investigated the unfolding property and rotational stability of a new toric intraocular lens (IOL); TECNIS toric II (toric-II, ZCW, Johnson & Johnson) that is an improved version of TECNIS toric IOL (toric-I, ZCV). Both IOLs are based on an identical platform, except for the frosted haptics with toric-II IOL. The study consisted of two parts; experimental study and clinical, retrospective, case series. Experimental study indicated that the overall time from IOL ejection to unfolding to 11 mm was significantly shorter with toricII than toric-I IOLs (p = 0.032), due to the earlier separation of the haptics from the optic with toric-II IOL. Clinical study included 131 eyes of 99 patients who had undergone phacoemulsification and toric IOL implantation. At 3 months postoperatively, toric-II IOL showed significantly better rotational stability than toric-I IOL, including smaller residual manifest astigmatism (p = 0.018), less amount of axis misalignment from the intended axis (p = 0.04), lower incidence of misalignment > 10º (p = 0.0044), and less degree of prediction errors (p = 0.043). Postoperative uncorrected distance visual acuity tended to be better in the toric-II than in the toric-I groups, with marginal statistical difference (p = 0.057). TECNIS toric II IOL with the frosted haptics showed significantly better rotational stability than its predecessor, probably due to quicker unfolding and greater friction with the capsular bag.

Aberration compensation strategy for the radius of curvature error of the primary mirror in off-axis three-mirror anastigmatic telescopes.

This paper discusses compensation strategies for the aberration fields caused by the error in the radius of curvature (ROC) of the primary mirror (PM) in pupil-offset off-axis three-mirror anastigmatic (TMA) astronomical telescopes. Based on the nodal aberration theory framework, the specific astigmatic and coma aberrations of the off-axis three-mirror system in the presence of the ROC error of the PM are derived. It is demonstrated that some field-dependent aberration components can be induced by ROC error in the off-axis TMA telescopes, apart from the dominating field-constant aberration terms. To reduce the influence of the ROC error on the aberration fields, we propose two aberration compensation strategies: adjusting the position of the PM and introducing axial misalignment of the secondary mirror (SM). Through theoretical analysis and simulations, we conclude that the compensation strategy of changing the axial position of the PM can make the aberration distribution close to the nominal state; the compensation strategy of axially adjusting the SM can make the aberration distribution meet the observation requirements, which is more suitable for space applications. We also discuss compensating the effect of the ROC error using lateral misalignments.

Influence of Heavy Weight Drill Pipe Material and Drill Bit Manufacturing Errors on Stress State of Steel Blades

Drilling volumes should be increased in order to increase hydrocarbon production, but this is impossible without the usage of high-quality drilling tools made of modern structural materials. The study has to analyze the design, technological and operational methods to increase the performance of drilling tools made of various materials and has highlighted prospects of technological method applications. The scientific novelty of the study consists in the development of a new analytical model of PDC drill bit–well interaction. The developed model takes into account the drill bit manufacturing errors in the form of bit body–nipple axes misalignment on the drill bit strength. This result makes it possible to determine the permissible manufacturing errors to provide safe operation of the drill bit. It is established that there is an additional transverse force that presses the drill bit to the well wall in the rock due to manufacturing errors. It is determined that the magnitude of this clamping force can be significant. The material effect has been analyzed on additional clamping force. It is established that geometric imperfection of the drill bit causes the minimal effect for the elastic system of the pipe string, which includes a calibrator and is composed of drill pipes based on composite carbon fiber material, and the maximal effect—for steel drill pipes. Polycrystalline diamond compact (PDC) drill bit and well wall contact interaction during operation in non-standard mode is considered. Non-standard stresses are determined, and the strength of the blades is estimated for different values of drilling bit manufacturing error.

Twelve-Wavelength-Switchable Thulium-Doped Fiber Laser With a Multimode Fiber Bragg Grating

In this article, a precisely controlled, switchable thulium-doped fiber laser (TDFL) with high optical signal-to-noise ratio (OSNR) is proposed and demonstrated. A home-made multimode fiber Bragg grating (MMFBG) with multireflection peaks was used as an optical filter to select the desired lasing channel. Using a manually controlled fusion splicer, the axial misalignment was applied between the single mode fiber and the MMFBG to switch the output wavelength. In the experiment, the number of switchable lasing lines was up to 12, and the fluctuation of the center wavelength and output power was less than 0.03 nm and 0.67 dB, respectively. A maximum slope efficiency of 1.3% was obtained when the axial misalignment was 0 μm, and the OSNR was higher than 65 dB. In addition, the proposed fiber laser was used as an optical fiber laser sensor to quantify the strain applied on the MMFBG, and a sensitivity of 1.16 pm/μ∈ was obtained.

Determination and Compensation of Axes Misalignment of Three-Coordinate Positioning Systems Using Acoustic Holography

Determination and Compensation of Axes Misalignment of Three-Coordinate Positioning Systems Using Acoustic Holography

Effect of some Disturbance Factors on Falling Point Distribution of Unguided Rocket

The paper investigates the individual and combined effects of disturbance factors including thrust misalignment, the offset of the centre of gravity and misalignment of the principal axes of inertia on falling point distribution of a type of unguided rocket (fin-stabilized rockets with single-stage solid-propellant rocket engines). The mathematical model used in the paper is developed from an available rocket motion model and solved for a representative rocket which is BM-21 rocket. The obtained results show dependencies of falling point deviation on disturbance parameters. These dependencies agree with the standard data given in the firing table; in addition, they are fuller and more insight ful than the previous research.

Effect of some Disturbance Factors on Falling Point Distribution of Unguided Rocket

The paper investigates the individual and combined effects of disturbance factors including thrust misalignment, the offset of the centre of gravity and misalignment of the principal axes of inertia on falling point distribution of a type of unguided rocket (fin-stabilized rockets with single-stage solid-propellant rocket engines). The mathematical model used in the paper is developed from an available rocket motion model and solved for a representative rocket which is BM-21 rocket. The obtained results show dependencies of falling point deviation on disturbance parameters. These dependencies agree with the standard data given in the firing table; in addition, they are fuller and more insight ful than the previous research.

Monocular Diplopia in Idiopathic Intracranial Hypertension: A Case Report and Literature Review.

Diplopia is the double vision of a single object, and can be binocular or monocular. Binocular diplopia is caused by the misalignment of the visual axes, with images falling on the fovea of the fixating eye and on the extra-foveal retina of the non-fixating eye, as a consequence of both neurological (i.e., oculomotor nerve palsies, ocular myopathies, neuromuscular junction disorders) and ophthalmic disorders (i.e., decompensation of a pre-existing strabismus). In contrast, monocular diplopia is generally explained by intraocular pathology (i.e., refractive errors, ocular media abnormalities, dry eyes), causing the image of a single object to fall, at the same time, on the fovea and on the extra-foveal retina of the same eye. We report the case of a 22-year-old woman presenting with acute-onset monocular diplopia. The diagnosis of idiopathic intracranial hypertension (IIH) was based on the presence of papilloedema and elevated cerebrospinal fluid (CSF) pressure. Monocular diplopia resolved after CSF subtraction. We describe a case of monocular diplopia as a presenting symptom of IIH, and discuss diagnostic issues of this possibly underestimated symptom in neurology clinical practice. Careful ophthalmic and neuro-ophthalmic examination can identify clinical features of diplopia, and drive diagnosis and treatment. Monocular diplopia is mostly an ophthalmological condition but can occur in a number of neurological diseases.Idiopathic intracranial hypertension can present with monocular diplopia.Differential diagnoses of diplopia in neurology and ophthalmology settings need to account for headache disorders.

Behavior of tunnels excavated with dip and against dip

Rock masses with remarked rock structure are likely to be highly anisotropic; thus, the relative orientation of the tunnel with respect to the rock structure will affect the tunnel behavior. Displacements measured at the walls of tunnels in highly anisotropic rock masses often reveal an asymmetric deformation pattern around the tunnel perimeter, which is often interpreted as the result of rock heterogeneity or changing geology. However, numerical and analytical investigation of tunnels in anisotropic rock masses show that the tunnel axis misalignment with the principal directions of stress and material anisotropy induce anti-symmetric axial displacements (i.e., axial distortion of the tunnel cross section) far behind the tunnel face. Near the face, the axial distortion is partially constrained, causing asymmetric radial displacements. In this study, tunnels excavated with and against dip of the major rock mass discontinuity are explored using 3D FEM modeling. A detailed analysis on the mechanisms associated with the direction of excavation is provided. It is shown that the asymmetric displacements near the face may strongly affect the displacements measured at the tunnel walls, which may explain the asymmetric displacements commonly observed on tunnels in anisotropic rock.

Clinical Study of Concomitant Strabismus.

Background and Objectives: Strabismus is a condition in which there is misalignment of visual axes of two eyes. Concomitant strabismus is a condition in which the angle of deviation is constant in all the directions of gaze. Concomitant strabismus is further classified as convergent, divergent, hyperdeviation and hypodeviation. Major presenting complaints include cosmetic blemish, diminution of vision, asthenopic symptoms like headache, eye strain and diplopia. This study was conceptualized to study the clinical and ophthalmological profile of patients with concomitant strabismus, in order to generate evidence to manage this condition more effectively. Material and Methods : This cross-sectional, observational study was conducted over a period of two years in 120 patients with concomitant strabismus. Ocular history and visual acuity were recorded. Cover, cover-uncover, alternate cover test, Hirschberg test, Krimsky test and examination by synaptophore were done. Refraction and fundus examination was also done. Result: Majority of the patients were under 5 years of age (46.6%) with male to female ratio of 2:3. Convergent squint was more common (71.6%) with majority of patients having moderate degree of deviation (58.8%). Hypermteropia was more commonly associated with squint (65%) more so with convergent squint. Eccentric fixation was present in only 10% of the cases. Conclusion: Convergent concomitant squint is more common type with majority of patients having moderate degree of deviation. Hypermetropia is more commonly associated with concomitant squint. Appropriate refraction and timely intervention can help in preventing amblyopia in young children

Automation of multi-modal beam focusing of an MeV sub-microprobe for ion beam analysis

We have developed an automatic beam-focusing system to reduce the experimental configuration time for a sub-micrometer-scaled beam probe of MeV ions with various analytical applications. Parasitic aberration due to misalignment and astigmatism must be eliminated or minimized to obtain an ideal beam spot size of less than 1 × 1 µm2, because astigmatism from excitation error and axial misalignment broaden the beam. The system involves a two-stage process of contrast and phase-difference detection that includes an automated minimization algorithm for astigmatism. The process can identify misalignments of axial rotation by measuring the line profiles of a fine mesh grid. The contrast method focused a proton microprobe to approximately 1 μm2 within 30 min, without the need for manual control when rotational misalignment was not present, while the phase-difference method successfully reduced the rotational error of lenses.

Eighty-Five Percent of Improved Optical Power Delivery to Epiretinal Prostheses Using Rigid Body Compensation Algorithm.

Vision impairment caused by degenerative retinal pathologies such as age-related macular degeneration can be treated using retinal implants. Such devices receive power and data using cables passing through a permanent surgical incision in the eye wall (sclera), which increases the risk to patients and surgical costs. A recently developed retinal implant design eliminates the necessity of the implant cable using a photonic power converter (PPC), which receives optical power and data through the pupil and is directed by an ellipsoidal reflector and micro-electromechanical mirror. We present a misalignment compensation algorithm model that accounts for rigid-body motions of the reflector relative to the eye and applies the correction to the mirror coordinates in the presence of angular misalignment of the reflector. We demonstrate that up to 85% of the nominal optical power can be delivered to the implant with axial reflector misalignments up to 30 deg using the compensation algorithm.

Influence of power-law fluid on transient performance of liquid film seal based on the time-dependent non-Newtonian dynamic Reynolds equation

The effects of lubricant's non-Newtonian property on dynamic characteristics of spiral groove liquid film seal are presented in this paper. The modified dynamic Reynolds equation for non-Newtonian fluid is derived, which is solved simultaneously with the kinematic equation. The transient response to the rotor's axial runout and angular misalignment, such as the axial and angular movement of stator ring, the transient film thickness, are presented for different power-law indexes, as well as the transient performance parameters. The results indicate that the seal has larger film thickness under the lubrication condition with dilatant lubricant while the stator ring has better tracking property operating with shear-thinning lubricant. Overall, the non-Newtonian property should be considered in the design of liquid film seal.

Five-Axis Machine Tool Volumetric and Geometric Error Reduction by Indirect Geometric Calibration and Lookup Tables

Abstract Modern CNC machine tools provide lookup tables to enhance the machine tool’s precision but the generation of table entries can be a demanding task. In this paper, the coefficients of the 25 cubic polynomial functions used to generate the LUTs entries for a five-axis machine tool are obtained by solving a linear system incorporating a Vandermonde expansion of the nominal control jacobian. The necessary volumetric errors within the working volume are predicted from the machine’s geometric errors estimated by the indirect error identification method based on the on-machine touch probing measurement of a reconfigurable uncalibrated master ball artifact (RUMBA). The proposed scheme is applied to a small Mitsubishi M730 CNC machine. Two different error models are used for modeling the erroneous machine tool, one estimating mainly inter-axis errors and the other including numerous intra-axis errors. The table-based compensation is validated through additional on-machine measurements. Experimental tests demonstrate a significant reduction in volumetric errors and in the effective machine error parameters. The LUTs reduce most of the dominant machine error parameters. It is concluded that although being effective in correcting some geometric errors, the generated LUTs cannot compensate for some axis misalignments such as EB(OX)A and EB(OX)Z. The root-mean-square of the translational volumetric errors is improved from 87.3, 75.4, and 71.5 µm down to 24.8, 18.8, and 22.1 µm in the X-, Y-, and Z-directions, respectively.

Rotational stability of modified toric intraocular lens.

We evaluated the rotational stability of a new toric intraocular lens (IOL), HOYA XY-1 toric IOL that is an improved version of HOYA 355 toric IOL, with longer overall length (13.0 mm vs. 12.5 mm), shortened unfolding time, and texture processing of the surface of haptics. Data from 193 eyes of 165 patients (76.4 ± 8.3 years old) with preoperative corneal astigmatism exceeding 0.75 diopters who had undergone phacoemulsification and toric IOL implantation were collected and analyzed. Corneal astigmatism, refractive astigmatism, and uncorrected (UDVA) and corrected distance visual acuity (CDVA) were evaluated before and 1 day, 1 week, and 1 month after surgery. The degree of IOL decentration, IOL tilt, and toric axis misalignment was assessed at 1 day and 1 month postoperatively. Fifty eyes received AcrySof toric IOL, 51 eyes TECNIS toric IOL, 46 eyes HOYA 355 toric IOL, and 46 eyes HOYA XY-1 toric IOL. The amount of axis misalignment from the intended axis was significantly different among IOLs (p = 0.004, one-way ANOVA), and HOYA XY-1 showed significantly less amount of axis misalignment than TECNIS (p = 0.020, Tukey’s multiple comparison) and HOYA 355 (p = 0.010). The proportion of eyes that showed axis misalignment <10° at 1 month postoperatively was significantly higher with HOYA XY-1 toric IOL than with other toric IOLs (χ2 test, p = 0.020). HOYA XY-1 toric IOL, the modified version of HOYA 355 toric IOL, showed excellent rotational stability in comparison with other models of toric IOLs.

Technological Solutions for Slant Directional Drilling Project Challenges

The paper describes an experience in the field of slant directional drilling in oil industry, which is currently under pressure. The experience helping to meet drilling projects’ challenges in an effective way has been approved for a several years of work at quite a few projects in different countries. The paper includes some design and technological tricks to overcome standard problems arising during slant directional drilling of oil wells such as entering the ground, maintaining the drilling trajectory, adjusting of an axis misalignment between the rig’s central shaft and the drill line, choosing proper pumps and adjusting pumping pressure, and keeping the drill rods and casings from sliding into the hole from an inclined mast.

Compact differential plane interferometer with in-axis mirror tilt detection

Besides the environmental fluctuations, the typical sources of significant uncertainty in the laser interferometry systems are the geometrical errors. These are stemming, among others, from the misalignment of measurement axes, the thermo-mechanical influences of the system components and the mounting, guidance errors of the translation mechanism that carries the measurement mirror or vibrations. We report on a compact double-pass differential plane interferometer that features an original optical arrangement with four parallel and coplanar beams, where the beam pairs in the two arms are coaxial. The differential arrangement minimizes the dead path and shortens the metrological loop so that the sensitivity to thermal drifts and vibrations is reduced. The arm symmetry allows for the preservation of the Abbe principle, and the common path mitigates the influences of the environmental disturbances. The interferometer optics is designed as a self-contained single-piece assembly made using optical contacting from the low-expansion materials. The interferometer system integrates the homodyne receiver (even though the optical arrangement is well-suited for heterodyne detection too) and also a tilt-detection electronics that allows for detection of pitch and roll of the interferometer mirror so that the parasitic movement of the measuring mirror could be compensated for. The experimental characterization revealed a good optical performance of the interferometer with sub-nanometre cyclic error and the resolution of tilt detection in order of a few microradians.