Misalignment Angle Research Articles

Experimental study and numerical simulation on the bearing behavior of the modified suction caisson under misalignment lateral cyclic and monotonic loadings

Suction caissons for offshore wind turbines are subjected to lateral misalignment wind and wave loads during service life, leading to the occurrence of accumulate deflection and changes in lateral bearing capacity. Experimental studies and numerical simulations were performed to investigate the motion mode, accumulated lateral deflection, and bearing capacity of a modified suction caisson (MSC) under misalignment lateral cyclic and monotonic loadings. Under misalignment lateral cyclic and monotonic loadings, the motion behavior of the MSC is combined with the translation, rotation, and torsion. The direction of MSC motion lies between cyclic and monotonic loading directions. The angle between the motion direction and cyclic loading direction is far less than that between the motion direction and monotonic loading direction. Under the same cyclic and monotonic load values, the maximum accumulated deflection was obtained when the angle between lateral cyclic and monotonic loading directions (which is defined as the misalignment angle) equals 30°. In addition, the lateral bearing capacity of the MSC after misalignment cyclic and monotonic loading was found to decrease with increasing the misalignment angle. The minimum lateral bearing capacity of the MSC after misalignment loading was obtained when the misalignment angle equals 180°. Based on the model test and simulation results, the method applying the model test results to the practical engineering is proposed.

Effect of adherends misalignment angle on bending strength of an adhesive joint: numerical and experimental results

ABSTRACT Bonded joints allow reducing the product weight and increasing fatigue resistance as compared to mechanical ones. Single-lap bonded joint (SLJ) is a simple example of this kind of joint. Literature focuses its attention on increasing the strength of SLJs; however, they do not consider the geometric deviations of the manufacturing process and used equipment, such as the adherends’ misalignment. This work presents a 3D numerical model that puts into relationship the adherends’ misalignment and the strength of a joint subjected to a 3-point bending test. The misalignment between the adherends was considered as the rotation of an adherend with respect to the other around two different axes. The 3D numerical model was also experimentally validated. To carry out the experimental tests, new equipment to accurately bond the adherends with a known value of misalignment between the adherends was designed, manufactured, and used. The experimental results are very similar to those obtained numerically by testifying a good agreement. The results show that the misalignment between the adherends decreases the bending strength the more the misalignment angle increases. The reduction ranges from 2% to 12% with the increase of the misalignment angle around an axis parallel or perpendicular to that of the adherends, respectively.

A fast alignment method for shipbore SINS with the aid of electro-optical detection system

Aiming at the challenge of the extensive initial alignment time required for small ship strapdown inertial navigation system (SINS) under swaying base on the sea, an alignment method aided by electro-optical detection system (EODS) is proposed. By employing the EODS to track a target on the shore with a known position, the relative distance and orientation to the ship are obtained as auxiliary information. A direct relation between the SINS misalignment angle and the error in target position estimation has been established. This method theoretically ensures a high observability degree for yaw misalignment. Simulation and semi-physical simulation indicate that the proposed method does not rely on an accurate initial attitude and is capable of rapid correction of a 5∘ yaw error. The use of two or more sets of EODSs and targets can further eliminate the necessity for precise positioning information. In semi-physical simulation, the yaw angle converges within 100 s, with the alignment accuracy reaching the upper limit determined by inertial measurement unit (IMU) precision. This method has potential engineering utility for scenarios such as rapid initialization of SINS on unmanned surface vehicles (USVs) in nearshore mooring conditions.

Experimental Investigation of the Yaw Misalignment Effect on the Power Performance and System Loading of a Flapping‐Foil Hydrokinetic Turbine

ABSTRACTHydrokinetic turbines (HTs) extract power by utilizing hydrodynamic forces from flow energy. The surplus load not used for power generation acts as a system load and must be considered when designing the turbine. Additionally, due to the variability of the flow direction during tidal power generation, the effect of the yaw misalignment angle on the power generation performance and system loading is an important design consideration. This study investigates the characteristics of an experimental model of an HT that uses two flapping foils, at different yaw misalignment angles through circulating water tunnel experiments. Experimental results show that with a yaw angle change of 10°, the power performance decreases by approximately 10% and the load increases by about 30% compared to an aligned configuration. Notably, the load in the flow‐perpendicular direction was significant, with periodic changes due to repetitive up‐and‐down motions. Consequently, the hydrodynamic force characteristics of the HT differ from those of conventional rotary turbines, necessitating the development of a design method that fits these characteristics for the actual installation of flapping‐foil HTs at tidal current power generation sites.

Thermal-Gas-Elastic Coupling Modeling and Performance Analysis of Foil Cylindrical gas Film Seal Considering Speed Slip, Temperature Jump and Shaft Misalignment

Abstract The Compliant foil cylindrical gas film seal is an advanced sealing technology designed for high-speed and high-temperature conditions in a jet engine. Its design involves using a compliant foil to create a cylindrical sealing surface, achieving adaptive sealing in environments with high pressure differences and rotational speeds. For high-speed and high-temperature operation, a speed slip flow model was established by considering film slip flow, wall temperature jump, foil deformation, and gas viscosity-temperature thermal effects. The variations in the lubrication performance of the foil cylindrical gas film seal with changes in shaft misalignment directions, misalignment angles, and operating parameters were investigated. The speed slip leads to a decrease in gas film lift and an increase in leakage. The wall temperature jump phenomenon caused by speed slip leads to a 2.56% decrease in film temperature. The shaft misalignment angles on the high-pressure and low-pressure sides have different impacts on the flow field, with film pressure and temperature differing by 66.78% and 11.19%, respectively.

Automatic Conditioning of Marine Seismic Angle Stack Data With a Convolutional Neural Network

Misalignment of reflections is a common problem in migrated prestack seismic data, which occurs due to moveout correction with incomplete knowledge of the velocity model. This issue persists in partial angle stack data often used for amplitude versus offset (AVO) analyses, and is traditionally treated with residual moveout and trim static corrections. However, these methods require time-consuming velocity selection and parameter tuning, and commonly lead to spurious alignment of reflections with noise. Therefore, we train a convolutional neural network (CNN) on synthetic examples to automatically perform conditioning and alignment of angle stack data. First, two-dimensional synthetic common depth point (CDP) gathers are created using a convolutional modeling method, and then made into input-target pairs where the inputs are poorly moveout-corrected (using inaccurate normal moveout velocities) and the targets are accurately moveout-corrected. These input-target examples are split into angle stacks for the near, mid, and far offsets, and then used to train a CNN to transform the misaligned angle stacks into their more-aligned counterparts. In testing, the trained network increases the alignment of unseen synthetic data, improving the correlation with the target far offset trace from 0.76 to 0.85 on average. The network is applied on two field examples from offshore Norway with Class 3 and Class 2P AVO responses, respectively. In both cases, the angle stack data predicted by the network shows improved alignment, greater resolution in the far offset stacked section, and increased correspondence to a well-tie synthetic seismogram, all while retaining the AVO responses. The CNN predictions are compared to angle stack data following traditional conditioning (residual moveout and trim static corrections), with the results being of similar or greater quality. This method enables high quality conditioning of angle stack data at a fraction of the time required for conventional methods, and is easily adaptable to different datasets.

Statistical characteristics of realistic fiber misalignments of unidirectional composites: Fitting distributions and scanning length effects

This paper presents a comprehensive study on the statistical characteristics of angle, tortuosity, curvature and wave magnitude to deepen the understanding of realistic fiber misalignments within unidirectional composites. A feasible fiber path reconstruction procedure has been optimized, which can be applicable to other types of composites. The high-resolution micrographs are acquired through X-ray computed tomography. The individual fiber segmentation is implemented using a U-Net deep learning method, and the fiber trajectories are reconstructed with the aid of a tracing algorithm. The stepped fiber trajectories are slightly smoothed and a polynomial fitting formula is adopted to quantitatively describe the fiber paths. The statistical characteristics corresponding to the differential tortuosity, misalignment angle, spatial curvature and wave magnitudes are comprehensively analyzed, with emphasis on their fitting distributions and scanning length effects. The collected data indicate that the statistical distributions of differential tortuosity and angle, curvature, and wave magnitude can be well fitted by normal, lognormal and Weibull equations, respectively. Particularly, the differential tortuosity and wave magnitude are overall features of individual fiber trajectory, which are highly correlated with the scanning length. In contrast, the angle and curvature are local features, so a smaller scanning length could obtain convergent results.

Numerical model and coupled vibration analysis of transmission shaft with spatial angle misalignment

Numerical model and coupled vibration analysis of transmission shaft with spatial angle misalignment

Torque Characteristics Analysis of Slotted-Type Axial-Flux Magnetic Coupler in the Misalignment State

In this article, a simple and practical magnetic equivalent charge model is proposed to predict the torque of a slotted-type axial-flux magnetic coupler (SAMC) under conditions of radial misalignment, angle misalignment, and synthetic misalignment. The magnetic field generated by the permanent magnet (PM) disk and the induced magnetic field generated by the slotted conductor sheet (CS) are equivalent to the surface magnetic charge, respectively. Particularly, the induced magnetic field produced by eddy current considering skin depth in the conductor sheet is introduced into the magnetic equivalent charge model. Combined with Coulomb’s law of magnetic field, the formulas of torque and axial force are both derived. Using this method, the torques in three cases of misalignment are calculated. Finally, the effectiveness of the model is verified by the finite element method (FEM) and experiment; the results calculated by the magnetic equivalent charge model are basically consistent with those from the finite element method and experiment. The derived formula is suitable for small air gaps, small slip rates, and small radial deflection distances. Additionally, the limitations of the method proposed are discussed, which is of great help for understanding the torque transmission of the magnetic coupler in the misalignment state.

Multiple Factors Causing Variability of Alignment in Childhood Concomitant Strabismus

Purpose: To investigate the potential factors related to variability of alignment in childhood concomitant strabismus. Design: Prospective inter-examiner (test-retest) reliability analysis. Methods: In total, 197 children with concomitant strabismus (57 esotropia, 140 exotropia) underwent repeat prism and alternate cover test (PACT) by two orthoptists who were certified by the study, and sensory tests were all performed once. We defined the alignment measurement as stable if the absolute value of the measurement difference between two orthoptists was within 10 prism diopters (PD), and unstable if the difference was 10 PD or greater. We analyzed the relationship between the measurement variability and sensory results, patient age, and angle of deviations. Results: The mean age of the esotropia and exotropia patients was 68.5 ± 26.3 months (range, 36–164 months) and 96.0 ± 33.7 months (range, 22–200 months), respectively, and there was a significant difference in suppression related variability of alignment, both at distance (P = 0.004) and at near (P = 0.046). Anisometropia also showed a significant difference at distance (P = 0.035) for variability of alignment, and there was no significant statistical effect of age on measurement variability in our study. Variability of alignment is positively associated with the angle of deviation, especially at distance (P = 0.021 for exotropia, P = 0.002 for esotropia) with more variability between observers with larger angles of misalignment. Conclusion: Suppression is an important factor for variability of alignment in childhood concomitant strabismus. Other factors, such as anisometropia and a large angle of strabismus should be taken into account when evaluating binocular alignment.

GNSS-assisted optimal alignment method for low-cost SINS motion of vehicle

Abstract To improve the alignment accuracy and environmental applicability of the micro-electromechanical system (MEMS)-based strapdown inertial navigation system (SINS), this study proposes a global navigation satellite system (GNSS)-assisted multi-vector determination of the attitude optimal indirect coarse alignment. Using the inertial information output from the inertial measurement unit and the velocity information from the GNSS, a simplified velocity observation vector is constructed and the velocity lever arm stemming from the mounting position inconsistencies of the GNSS and SINS is fed back into the velocity of the carrier system. When constructing the observation vectors, the integration interval is shortened by reconstructing the two-vector integration formula for reducing the cumulative error of the inertial device. The attitude matrix problem is defined as the Wahba problem, which is solved using the singular value decomposition method. Based on the relationship between gyro zero bias and misalignment angle, the corresponding state and measurement equations are designed. Furthermore, owing to the measurement noise uncertainty, the adaptive traceless Kalman filtering algorithm is introduced to realize the effective adaptation processing of the measurement noise. More accurate attitude matrix estimates are obtained by continuously correcting the carrier system transformation matrix. The running car experiment results show that the proposed method exhibits higher alignment accuracy and environmental applicability than the current MEMS strapdown inertial navigation coarse alignment method and the traditional optimization-based alignment method.

Dynamic responses of monopile offshore wind turbines under different wind-wave misalignment angles

Wind-wave misalignment is a common occurrence for monopile offshore wind turbines during extreme typhoon conditions. This phenomenon has a significant impact on the structural dynamic response of turbine structures and poses a threat to their structural integrity. In this study, finite element analysis is conducted on 75 sets of working conditions of monopile offshore wind turbines to investigate their dynamic response under different wind turbine operating states, wind-wave misalignment angles, and randomness of wind and wave load conditions. The results of the analysis indicate that the impact of wind-wave misalignment angles on the dynamic response of the monopile offshore wind turbine varies depending on the operational conditions. Furthermore, the study reveals that there are variations in the dynamic response of the monopile offshore wind turbine under different combinations of wind and wave loads. During the parked state and yaw system fault of the monopile offshore wind turbine, the most adverse working conditions need to consider wind-wave misalignment angles of 0° and 180°. In contrast, the most adverse working conditions for operational states emerge when the wind-wave misalignment angle is 90°. These findings highlight the importance of considering wind-wave misalignment angles and the randomness of wind and wave load conditions when assessing the dynamic response and structural integrity of monopile offshore wind turbines.

Effects of foundation pit excavation on adjacent metro stations and shield tunnel structures: a study on horizontal displacement

PurposeThe aim of this study is to investigate the horizontal displacement effects of foundation pit excavation on adjacent metro stations and shield tunnel composite structures. It seeks to develop a theoretical calculation method capable of accurately assessing these engineering impacts, aiming to provide practical assistance for engineering applications.Design/methodology/approachThis study introduces a model for shield tunnel segments incorporating rotation and misalignment, considering the constraints of metro stations. It establishes a displacement model for tunnel-station combinations during foundation pit excavation, deriving a formula for calculating station-proximal tunnel horizontal displacements. The method's accuracy is validated against field data from three engineering cases. The research also explores variations in tunnel displacement, inter-ring shear force, misalignment and rotation angle under different spatial relationships between pits, tunnels and stations.FindingsThis study models uneven deformation between stations and tunnels due to bending stiffness and shear constraints. It enhances the misalignment model with station-induced shear effects and introduces coefficients for their mutual interaction. Results show varied responses based on pit-station-tunnel positioning: minimal displacement near pit edges (coefficients around 0.1) and significant effects near pit centers (coefficients from 0.4 to 0.5). “Whip effect” from station constraints affects tunnel displacement, shear force, misalignment and rotation, with fluctuations decreasing with distance from excavation areas.Originality/valueThis study demonstrates significant originality and value. It introduces a novel displacement model for tunnel-station combinations considering station constraints, addressing theoretical calculations of horizontal displacement effects from foundation pit excavation on metro stations and shield tunnel structures. Through validation with field data and parameter studies, the concept of influence coefficients is proposed, offering insights into variations in structural responses under different spatial relationships. This research provides crucial technical support and decision-making guidance for optimizing designs and facilitating practical construction in similar engineering projects.

A robust iterative algorithm for SINS/USBL integrated navigation based on dual hydrophone differential model

Aiming at the complex underwater environment which leads to large measurement errors and outliers in ultrashort baseline, a robust iterative Kalman filtering algorithm based on the differential model of dual hydrophones is proposed in this paper. Firstly, to achieve accurate navigation under large initial misalignment angles, the algorithm builds an inertial navigation error equation based on the right invariant error definition of Lie groups. Then a dual hydrophone differential model is proposed based on SINS/USBL tightly coupled. It successfully improves the accuracy of integrated navigation and significantly mitigating the issue of SINS/USBL positioning accuracy degradation caused by USBL slant distance noise that grows with distance. Finally, a robust iterative Kalman filter based on the dual hydrophone differential model is proposed to counter the threat to the vehicle’s safe operation and the accuracy loss caused by outliers. The algorithm’s superiority and effectiveness are verified through simulation and sea trial.

Full-wave simulations on helicon and parasitic excitation of slow waves near the edge plasma

Helicon waves are thought to be promising in various tokamaks, such as DIII-D, because they can penetrate reactor-grade high-density cores and drive the off-axis current with higher efficiency. In the frequency regime ∼ 476 MHz, both slow electrostatic and fast electromagnetic helicon waves can coexist in DIII-D. If the antenna parasitically excites the slow mode, these waves can propagate along the magnetic field line into the scrape-off layer (SOL). Although the importance of the misalignment of the Faraday screen and the electron density in the SOL on the excitation and propagation of slow modes is well known, the conditions for minimizing slow mode excitation have yet to be optimized. Using the Petra-M simulation code in the 2D domain, we analyze the effects of the misalignment of the antenna in the poloidal direction, the misalignment of the Faraday screen in the toroidal direction, and the density in front of the antenna on slow mode generation. Our results suggest that the misalignment of the Faraday screen is a critical factor in reducing the slow mode and that the misalignment angle should be below ∼ 5° to minimize the slow wave excitation. When the electron density is higher than 3.5×1018 m−3 in the SOL, the generation of the slow mode from the antenna is minimized and unaffected by the misalignment of the Faraday screen.

LoVoCCS. II. Weak Lensing Mass Distributions, Red-sequence Galaxy Distributions, and Their Alignment with the Brightest Cluster Galaxy in 58 Nearby X-Ray-luminous Galaxy Clusters

The Local Volume Complete Cluster Survey is an ongoing program to observe nearly a hundred low-redshift X-ray-luminous galaxy clusters (redshifts 0.03 < z < 0.12 and X-ray luminosities in the 0.1–2.4 keV band L X500c > 1044 erg s−1) with the Dark Energy Camera, capturing data in the u, g, r, i, z bands with a 5σ point source depth of approximately 25th–26th AB magnitudes. Here, we map the aperture masses in 58 galaxy cluster fields using weak gravitational lensing. These clusters span a variety of dynamical states, from nearly relaxed to merging systems, and approximately half of them have not been subject to detailed weak lensing analysis before. In each cluster field, we analyze the alignment between the 2D mass distribution described by the aperture mass map, the 2D red-sequence (RS) galaxy distribution, and the brightest cluster galaxy (BCG). We find that the orientations of the BCG and the RS distribution are strongly aligned throughout the interiors of the clusters: the median misalignment angle is 19° within 2 Mpc. We also observe the alignment between the orientations of the RS distribution and the overall cluster mass distribution (by a median difference of 32° within 1 Mpc), although this is constrained by galaxy shape noise and the limitations of our cluster sample size. These types of alignment suggest long-term dynamical evolution within the clusters over cosmic timescales.

In-motion fine alignment algorithm for AUV based on improved extended state observer and Kalman filter

Abstract Achieving fast initial alignment has always been a major challenge for autonomous underwater vehicle navigation, especially in motion. During the fine alignment process, traditional algorithms often face the slow convergence of the azimuth misalignment angle. To solve this problem, this paper proposes a fast alignment algorithm based on the improved extended state observer (ESO) and Kalman filter. Specifically, since the application potential of ESO in fine alignment has not been fully explored by previous studies, this paper introduces the improved ESO through the in-depth research of traditional ESO. The obtained improved ESO is then combined with Kalman filter to constitute the proposed fast alignment algorithm. The algorithm first uses Kalman filter to estimate the two horizontal misalignment angles. Once the horizontal angles estimation of Kalman filter tends to be stable, the improved ESO is used to estimate the azimuth misalignment angle. Simulation and lake test show the proposed algorithm has excellent performance of in-motion alignment. The comparative analysis shows that the algorithm significantly improves the convergence speed of azimuth alignment angle.

Advanced Characterization of the Spatial Variation of Moiré Heterostructures and Moiré Excitons.

In this short review, an overview of recent progress in deploying advanced characterization techniques is provided to understand the effects of spatial variation and inhomogeneities in moiré heterostructures over multiple length scales. Particular emphasis is placed on correlating the impact of twist angle misalignment, nano-scale disorder, and atomic relaxation on the moiré potential and its collective excitations, particularly moiré excitons. Finally, future technological applications leveraging moiré excitons arediscussed.

A novel layup process for reducing surface thermal distortion of CFRP laminate reflector

This study proposes a novel anti-symmetric folding layup process to reduce the surface thermal distortion of carbon-fiber-reinforced polymer (CFRP) reflector. Firstly, theoretical equations regarding the influencing factors of surface thermal distortion in CFRP reflector are derived, and the concept and advantages of the anti-symmetric folding layup process are introduced. Secondly, free thermal expansion analysis considering the ply angle misalignment is conducted, showing that the novel process can reduce surface thermal distortion by 36.13 % compared to traditional process. Finally, experimental samples with different layup processes are designed and manufactured, and their surface thermal distortion is detected using shear speckle interferometry. The experimental results show that compared with the traditional symmetric layup process, the double anti-symmetric folding layup process can reduce the surface thermal distortion of CFRP reflector by 32.39 %, demonstrating significant advantages in thermal stability and strong potential for practical engineering applications.

Effect of Small Angle Misalignments on Ocular Wavefront Zernike Coefficients

Purpose: To assess the possible impact of minor changes in fixation on wavefront measurements as a potential constraint in detecting subtle temporal variations in ocular wavefront error. Methods: Twelve healthy subjects with an average age of 36.3 ± 8.8 were instructed to put their heads in the aberrometer’s chin-rest and look at a fixation target that was embedded in the device. The fixation targets were readily observable to the participants without accommodation, thanks to the aberrometer’s Badal system. When each eye was staring at the target, its wavefront aberration was recorded three times and then averaged for further analysis. The averaged Zernike coefficients were rescaled to the smallest value of the maximum round pupil found among all eyes (4.41 mm), and this procedure was repeated for each target. Results: Alteration of the fixation targets caused changes to the Zernike coefficients of defocus (C(2,0)), vertical trefoil (C(3,–3)), vertical coma (C(3,–1)), horizontal coma (C(3,1)), oblique trefoil (C(3,3)), primary spherical aberration (C(4,0)), and secondary spherical aberration (C(6,0)), but the changes were not statistically significant. Nevertheless, an alteration in the target’s size and shape exhibited a significant correlation across all of the aforementioned coefficients in both eyes (p &lt; 0.05). The total RMS of aberrations and the RMS of the spherical-like aberrations were both lowest while choosing the larger Maltese cross, and the bigger E-letter minimized the RMS of HOA and comatic aberrations. Conclusion: The aberrometric changes occur as a consequence of altering the fixational gaze and are within the range of the changes found after performing a near-vision task, so they might potentially act as a confounding factor when attempting to identify such small variations in the ocular wavefront. Using a smaller E-letter (5 arcmin) as an internal fixation target resulted in the least standard deviation of measurements, fixational stability, and higher accuracy in ocular wavefront measurements.