Explore the vast range of titles available.

When detecting positive selection in proteins, the prevalence of errors resulting from misalignment and the ability of alignment filters to mitigate such errors are not well understood, but filters are commonly applied to try to avoid false positive results. Focusing on the sitewise detection of positive selection across a wide range of divergence levels and indel rates, we performed simulation experiments to quantify the false positives and false negatives introduced by alignment error and the ability of alignment filters to improve performance. We found that some aligners led to many false positives, whereas others resulted in very few. False negatives were a problem for all aligners, increasing with sequence divergence. Of the aligners tested, PRANK's codon-based alignments consistently performed the best and ClustalW performed the worst. Of the filters tested, GUIDANCE performed the best and Gblocks performed the worst. Although some filters showed good ability to reduce the error rates from ClustalW and MAFFT alignments, none were found to substantially improve the performance of PRANK alignments under most conditions. Our results revealed distinct trends in error rates and power levels for aligners and filters within a biologically plausible parameter space. With the best aligner, a low false positive rate was maintained even with extremely divergent indel-prone sequences. Controls using the true alignment and an optimal filtering method suggested that performance improvements could be gained by improving aligners or filters to reduce the prevalence of false negatives, especially at higher divergence levels and indel rates.

Purpose The purpose of this study was to detect the pre- and intra-operative influential factors for lower limb alignment correction error in open-wedge high tibial osteotomy (OWHTO). Methods This study involved 69 patients (71 knees) undergoing OWHTO for primary medial osteoarthritis. The weight-bearing line (WBL) ratio, medial proximal tibial angle (MPTA), and joint line convergence angle (JLCA) were measured on radiographs preoperatively and at 1 month after surgery, and the differences between the pre- and postoperative values were calculated. The correction angle during surgery was also investigated. The radiological correction angle was defined as the difference between the pre- and postoperative MPTA. The correction error was defined as the difference between the correction angle during surgery and the radiological correction angle. The ideal correction angle was defined as when the postoperative WBL passed through Fujisawa’s point (WBL = 62.5%), and the alignment error was defined as the difference between the postoperative WBL ratio and 62.5. The correlations among the alignment error, the correction error, correction angle during surgery, pre- and postoperative WBL ratio, MPTA, and JLCA and the differences between the pre and postoperative WBL ratio, MPTA, and JLCA were investigated. In addition, the factor most influential on the alignment error was determined. Results The preoperative MPTA was the only predictor of the alignment error after OWHTO. The alignment error was positively correlated with the correction error and correction angle during surgery, and negatively correlated with pre- and postoperative WBL ratio, MPTA, and differences between the pre- and postoperative WBL ratio and JLCA. Conclusion The preoperative MPTA was the only pre- and intra-operative predictor of the alignment error after OWHTO. The larger the correction angle, the greater the alignment error. The MPTA was recommended as an indicator for improving the correction accuracy. Accurate correction based on the MPTA provides good lower limb alignment and better clinical results. Level of evidence III Case–control study/Retrospective comparative study.

As key components to transmit power and motion between intersecting shafts, it is necessary to design feasible tooth axial modification to improve the meshing performance and bearing capacity of straight bevel gears. The main purpose of this paper is to propose an effective axial modification method of straight bevel gears considering alignment errors. In this paper, the meshing performance of two kinds of tooth axial modification method (tooth end relief and symmetric crowned modification) for straight bevel gears is investigated by the finite element analysis (FEA). The results show that the tooth end relief is an optimal method to enhance the meshing performance of gears in different installations for decreasing transmission errors, reducing maximum contact stress and bending stress and improving the distribution of contact stress and bending stress. This research provides a suitable tooth end relief method of straight bevel gear with alignment errors.

The fiber mode field overlap integral method is employed to analyze the influencing factors of coupling efficiency, as well as the effects of axial and radial alignment errors on coupling efficiency under different relative apertures of coupling lenses. The results indicate that there exists an optimal relative aperture of the coupling lens that maximizes coupling efficiency; however, at this optimal point, coupling efficiency is more susceptible to radial errors. Regarding axial and radial errors, when the relative aperture of the coupling lens is at its optimal value, the tolerance for alignment errors is minimal. Conversely, when the relative aperture exceeds the optimal value, both coupling efficiency and tolerance for alignment decrease. When the relative aperture is less than the optimal value, the requirement for installation accuracy decreases while the tolerance becomes larger. The trend of the simulation results aligns with the experimental data. This study provides instructive significance regarding the trade-off between coupling efficiency requirements and alignment accuracy in the design of actual polarization-maintaining fiber coupling systems.

The Talbot wavemeter has attracted widespread attention from researchers in recent years due to its advantages of miniaturization and low cost. However, the impact of varying incident conditions caused by factors such as alignment has remained a challenge for spectral retrieval. This paper first derives the influence of different incident conditions on the interference pattern based on Fresnel diffraction and verifies the derivation through simulations. We propose a method to address the impact of incident conditions on the interference pattern. By adding a grating with a different periodicity in front of the detector, Moiré fringes are generated in the periodicity dimension, increasing the fringe period and thus enlarging the tolerance for angular misalignment. Finally, we constructed a Talbot wavemeter based on a double-grating structure, achieving a spectral resolution of 9 nm at 360 nm. This method provides a reference for the future development of a high-precision, high-resolution Talbot wavemeter.

This study concerns the strapdown inertial navigation system (SINS) initial alignment under marine mooring condition with large initial error. The ten-dimensional state initial alignment error functions of the SINS with inclusion of non-linear characteristics have been derived. It is pointed out for the first time that the non-linear functions are applied to only a subset of the elements of the state vector, that is, the velocities error and the misalignment angles. Then a computationally efficient refinement of the unscented transformation (UT) called marginalised UT (MUT) is investigated in these special non-linear systems with a linear substructure. A performance comparison between the extended Kalman filter (EKF), the UT-based Kalman filter (UKF) and the MUT-based Kalman filter (MUKF) demonstrates that both the UKF and the MUKF can outperform the EKF and the MUKF and can achieve, if not better, at least a comparable performance to the UKF, at a significantly lower expense.

This paper describes a method for calibrating in-plane center alignment error (IPCA) that occurs when installing the circular motion slide (CMS). In this study, by combini ng the moving carriage of the CMS and the planar PKM (parallel kinematic mechanism) with the machine tool, the small workspace of the PKM is expanded, and the workpiece is placed on the table with the CMS installed is processed through the machine tool. However, to rigidly mount the CMS on the table, the preload between the guide and the support bearings must be adjusted with the eccentric bearing, and in this process, the IPCA occurs. After installing a reflective marker on the PKM, the PKM is slowly rotated along with the ring guide in the way of stop-and-go without the PKM’s own motion. Then, using a machine vision camera installed at the top of the CMS, the IPCA, which is the difference between the actual center position and the nominal center position of the CMS with respect to the camera, can be successfully calibrated through the circular fitting process. Consequently, it was confirmed that the IPCA of 0.37 mm can be successfully identified with the proposed method.

The beam angle error of the pump light in a K-Rb-21Ne spin-exchange relaxation-free atomic co-magnetometer (SERFCM) significantly degrades the efficiency of optical pumping and the system’s ability to suppress magnetic field noise. In this work, a system response model that incorporates the pump beam alignment error (PBAE) is established. The influence of PBAE on the scale factor, bandwidth, and magnetic noise response of the inertial output is analyzed. Theoretical results show that PBAE increases the internal magnetic field gradient, reduces the efficiency of nuclear spin hyperpolarization, and increases the nuclear spin relaxation rate, ultimately degrading the system’s scale factor, bandwidth, and magnetic noise suppression capability. Experimental results demonstrate that, compared to the original SERFCM with PBAE, aligning the pump laser using the proposed method improves the polarization strength of nuclear spins by approximately 10% and enhances magnetic noise suppression by 40%.

This article presents a high precise deployment mechanism for a deployable space telescope to facilitate satellite miniaturization. It is designed with a passive deployment mechanism utilizing a spring hinge. In particular, the customized modules and an assembly jig are specifically designed to reduce alignment errors. To confirm the feasibility of the designed mechanism, three alignment errors that influence the optical performance of the structure—tilt, de-center, and de-space—are theoretically analyzed for quarter, half, and full model, respectively. In the case of quarter model, significant results are obtained as a tilt of 21.12 µrad, a de-center of 2.20 µm, and a de-space of 1.71 µm. Based on the theoretical analysis, a deployment mechanism of the quarter model is fabricated, and the alignments of the deployment mechanism are experimentally investigated with a measurement platform consisting of five non-contact-based laser displacement sensors. In addition, the influence of gravity on the alignment error is analyzed and compensated by investigating the tendency of the alignment error according to the rotation degree of the measurement model for the direction of gravity. As a result of the gravity compensation, the proposed mechanism gives acceptable alignment errors as a tilt of 30.04 µrad, de-center of 8.92 µm, and de-space of 4.03 µm, which are controllable by employing the conventional focusing mechanism.

In the field of compressed imaging, many attempts have been made to use the high-resolution digital micromirror array (DMD) in combination with low-resolution detectors to construct imaging systems by collecting low-resolution compressed data to reconstruct high-resolution images. However, the difficulty of achieving micrometer-level alignment between DMD devices and detectors has resulted in significant reconstruction errors. To address this issue, we proposed a joint input generative adversarial network with an error correction function that simulates the degradation of image quality due to alignment errors, designed an optical imaging system, and incorporated prior imaging system knowledge in the data generation process to improve the training efficiency and reconstruction performance. Our network achieved the ability to reconstruct 4× high-resolution images with different alignment errors and performed outstanding reconstruction in real-world scenes. Compared to existing algorithms, our method had a higher peak signal-to-noise ratio (PSNR) and better visualization results, which demonstrates the feasibility of our approach.